A beautiful, remote and culturally rich country infamous for its military regime, Myanmar (Burma) has in recent years been making small steps towards democracy, with the first democratically elected government in 2015, after more than half a century.

One will still encounter men wearing the sarong-like longyi and chewing betel nut, spitting the blood-red juice onto the ground, women with faces smothered in thanakha (a natural sunblock), and cheroot-smoking grannies. Trishaws still ply city streets, while the horse or bullock and cart is common rural transport.

-----

We carefully planned our 3-weeks long Burmese adventure around 6-days long hiking trip in the remote Chin state, where we commenced our journey in the hilltop settlement of Mindat, and subsequently hiked for four days across ethnic minority villages using old footpaths and mule trails.

Besides that, Bagan was the obvious spot to spend a few days exploring its temples, and we also spent a few days more in the south around Hpa-An. Then, finally, Ngapali was the ultimate destination for our beach leisure time.

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Don't forget your sunblock in Peru...

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Who wants to help put on the sunblock?

Really - I can't believe I've lived here for 3 1/2 years and not done this shot yet.

Another cliche checked off the list.

sunbathing on the amstel

Day 29 - In honor of Memorial Day, here's a two-for-one special! My Hello Kitty beach bag that I bought in Florida AND my new Hello Kitty flip-flops! Who's ready for the beach?!

Beach bag - Sanrio, 2004

Flip-flops - Sanrio, 2011

And this is the reason you should wear sunblock!!

"Always use plenty of sunblock!"

View Complete Story on thescarcitycollective.myshopify.com/blogs/news

Bicycle glamping. That’s what we’ll call it.

Our Adventure Vibes 2 bicycle camping trip started, oddly enough, in the car. The group had only coalesced around the idea of camping mid-week, propelled by the argument that Robby would soon have a job again and Sam and Mary Ellen were leaving the next weekend. Unfortunately, due to the beautiful weather and the Florida Ironman, camping spots were limited. Top picks Topsail and Grayton Beach State Park were full, which meant a last-of-the-season beach camping trip was out. Since we were riding with a couple of casual riders (me and Jennifer) and a couple of fit non-riders (Sam and Mary Ellen) the options were also constrained by distance. So Jennifer, Robby and I loaded up our car and drove north on 79 in the hopes that we would grab a first-come first-served camping spot at Pine Log State Forest early Friday morning.

As we drove through the campsite, we were increasingly dismayed by the “Reservation Only” signs posted prominently on each site. One by one we passed the prime camping spots on the pond, until we finally reached the last two sites. The only sites that didn’t require reservation. Sites 19 and 20. And site 19 had a RV, and it looked like it had been there all summer. With pleading eyes we glanced as one at Site 20.

Empty.

With a collective sigh of relief, since the whole trip was riding on our securing a site, we pulled in and jumped out, unloading all of our gear with speed since we were already a little behind, and we needed to get back in time to meet with Sam and Mary Ellen (henceforth known as Sam-Ellen for brevity’s sake. or Mary-Sam. But don’t tell Mary-Ellen’s mom).

Leaving all of our precious and heavy gear behind, we sped south again to drop Robby off in time to drink coffee and eat before he headed over the bridge to meet us down in the Cove, where we’d set off to Lynn Haven to meet with Sam-Ellen.

We agreed on 10. At 10:15 I texted Robby. At 10:30 he rolled in, sweating in the only mildly warm air of late October.

“I got stuck waiting on a train,” he smiled, not breathing heavy despite the obvious speed of his journey.

“So I went around.”

We assured him it was no problem as I shot a text to Mary-Sam and we finally set off, barely carrying any gear but sunblock and Robby’s Bluetooth speakers. Don’t worry, this was not the same speaker than only lasted 10 seconds on our last trip. Maybe, I dreamed, the speakers would last a whole song.

Five miles north on 77 and we approached the Wal-Mart area where we’d planned to meet up with Sam-Ellen.

Mary-Ellen is the sister of last adventure’s hero, J.Michael. Compound names are a family trait, although Mary-Ellen and Michael are different in other, less obvious ways.

Mary-Ellen and Sam were in town, having just returned from Spain where they did something nefarious for a year to make ends meet, strung together by shoe string trips to Mallorca for volley ball tournaments. There were rumors of mafia activity. Or weapons trafficking. J. Michael would be joining us later in the evening after work, but Mary-Sam were borrowing bikes, and ominously, his saddles for the trip. They were also loaded down with fresh fruit and vegetables, along with a great deal of grouper for dinners.

We spotted Sam-Ellen by the side of the road and met up briefly before deciding to hit the Wally World for supplies. And because Robby had forgotten to eat. We mentioned there was a Subway in the Wal Mart, so Robby headed for food while we got other needed items.

When we got back to the bikes were Sam was standing guard in one of Mary-Ellen’s bright yellow tournament tank tops, impressively tanned guns on full display, we realized Robby had completely missed the Subway and instead bought mac-n-cheese and barbeque chicken.

At one point as Robby scarfed down his food hurriedly, I glanced over and noticed he was leaning on the nearby grocery carts as he ate, not remotely seeming to enjoy the meal. He laughed and packed up the leftovers for later.

At last we pulled out heading north again, on 77, before wheeling off onto a side road to ride through less heavily trafficked neighborhoods until we reached the Bailey bridge.

We cruised merrily along in a loose formation through shaded suburbs. The sun was bright but the air was not yet hot. Suddenly, our peaceful ride was thrown asunder, as Mary-Ellen, riding with Sam at the rear the five ship formation, shrieked.

Just then, a squirrel darted from a well-manicured lawn, hell bent for the sweet release of a rolling bike tire. With no time to react, Robby’s death machine continued forward as the tan flash of fur darted right into his wheels, its head wedging into a spoke, spinning him around and casting him out like a weak child from a merry go ‘round. Just milliseconds later, Sam’s bike rolled right over the poor rodent with a quick thump thump.

In shock, we rolled on for half a block until we turned back to look, jabbering, aghast at what had just happened.

There, in an ironic pocket of sunlight, dead center in the middle of the unlined street, lay the squirrel, twitching and writhing, unable to run away.

“Should we do something?”

“We should at least move it from the road,” Mary Ellen suggested, taking the moral lead.

We all agreed.

We slowly approached the still spasming vermin.

“Should we kill it?”

“Yeah, snap it’s neck.”

“I don’t know if I can do that.”

“Let’s just move it off the road.”

Mary-Ellen knelt, gently touching it’s fur, which seemed to calm it.

She reached carefully under his heaving torso and lifted him, cradling him to her chest. Pacified, it seemed to grip her fingers, as if holding on to life.

The rest of us stood transfixed.

After a few moments, Mary-Ellen placed the squirrel in the grass near a shrub in the hopes that it might recover a bit, or at least die with the dignity it would be denied in the middle of the asphalt strip that had been its reckoning.

Someone shifted the feet, and the squirrel shockingly leapt nimbly a few steps before stopping.

We were all amazed it had moved, seemingly without injury.

Finally, it leapt ever farther away, quickly and with vigor.

As we moved away, we were all relieved to see it dash up a pine tree. He would live after all!

Or die out of sight. Either way, our conscious was clear.

With dazed but lifted spirits we hit the road again, heading north with all the speed our ragamuffin group could manage.

5 miles up the road or so, we stopped off after an uneventful stretch at a Dollar General to refill water and snack on ice cream before continuing on our journey. It was now officially hot, and the route was decidedly not shady. Robby turned the speakers on and we were propelled to the beats of gangster rap and techno-pop, or something like that anyway.

We finally turned west on highway 20 where we began to see Ironman markings on the road, and where 20 miles or so into the 30 mile trip, Sam had to wrap J.Michael’s much beloved Brooks saddle in towels to aid his ailing buttocks.

At last, as the sun approached the horizon, we turned onto 79 to head 1 more mile to Pine Log after a quick stop at the convenience store.

It was downhill, so we were moving nicely until Sam had to stop as Tupperware’s full of some exotic homemade hummus tumbled off his rack, which went unnoticed by Robby who kept right on rolling, feet tucked on the top tube as he descended the gentle slope towards the state park.

After securing his load, we restarted the final stretch, before Mary-Ellen struck a sharp rock, puncturing her narrow road tires. The slow leak allowed us to arrive at the dirt road entrance before it finally gave way. And so, unceremoniously and 5 hours later, we arrived walking our bikes.

We arrived just before sundown, so with only a few minutes of light left, we set about gathering firewood. Robby began darting like an enlivened forest hermit through the fringes of the surrounding pine forest. As I grabbed dead branches and small sticks, the quiet evening campsite was filled with the cracking and thrashing of entire logs being pulled across the gravel road and into the campsite. Robby dropped the logs one by one and bounded back into the dim dusk to find more.

Meanwhile, Sam-Ellen set about arranging their campsite, while Jennifer likewise began to prep dinner. Katie was inbound from PCB in Robby’s car with more supplies, and J.Michael would soon be getting off work and setting out to join us. With a pretty large pile of firewood, or wood at least, Robby and I also happened upon a stack of pre-cut wood that may or may not have been free for anyone to use, but somehow made its way into our site.

With the last bit of light, Mary-Sam set up their slackline and began to balance as best they could on tired legs and frazzled minds after a long, hot ride. And like that, the sun dipped below the bunched tree tops of the swaying pines, reappeared intermittently between the thin trunks, and at last fell below the horizon.

Katie finally arrived, but the gate code we’d been given was wrong, so as we tried to figure out the best way to get the correct code, while also squirreling away the aforementioned pre-cut, maybe-free wood, Katie befriended a kind elderly gentleman, who turned out to be the camp host. He revealed the correct code, which we’d reversed, and she truly arrived.

As we ate, J.Michael called to complain to Mary-Ellen about the bike he’d been left with, the gear he had or didn’t have, and most significantly, the headlight Sam had accidently taken, leaving J.Michael with no light to make the 30+ mile journey from Lynn Haven. Over the next couple of hours, we got cryptic, half-finished texts from J. Michael about his whereabouts, until he emerged suddenly out of the darkness, sweaty and clearly a tad bit irritated. He stopped abruptly when he was nearly closelined by the slack line, strung waist high between two stout trees, before anyone could warn him.

J. Michael had ridden all the way in the dark...well, all the way from the airport, where his mother had graciously dropped him, anxious to have him out of the house for her own date night. But still, 15 miles on 388 and 79 with zero light on a new moon...ghastly.

His first act was to remove the headlight from Sam’s borrowed bike and put it on his.

“How’d you do it, Michael,” someone asked.

“I mostly just tried to be a disembodied spirit.”

With the full cast assembled, the rest of the night was passed in increasingly drunken revelry, lit only by a very bright spotlight Robby brought and the crackling camp fire. We pulled the picnic table close to the fire and played Cards Against Humanity and Exploding Kittens until it was well past midnight, stopping only to eat too many s’mores.

Jennifer and I had rented cots from the Navy Base and only discovered after arrival at Pine Log that they didn’t fit in our tent, so we slept out under the stars and froze, eventually sharing one cot in uncomfortable, cramped misery.

It would be much colder night two.

Saturday broke cool and clear, and we all awoke in our own time. Michael first with his quiet yet penetrating voice and clicking clipless shoes, followed by Jennifer and I. We made breakfast, trying to be quiet, until Robby and Katie awoke, followed by a sarong’d Sam, and Mary Ellen. Before breakfast, they slacklined, the equilibrius envy of Robby, who tried himself later in the morning, after his birthday breakfast of mimosas and steak as prepared by Katie.

After breakfast, J.Michael, Jennifer and I ventured out to the nearby gas station for snacks, only to find ourselves smack dab in the middle of Ironman Florida. Despite our garb of straw and trucker hats, casual clothing, and mountain bikes, the eager volunteers offered us water and bananas.

On the way back we were passed by several leaders of the race, one of whom J.Michael attempted to keep up with on his fixie. He was going to win, too, but he was stung by a mysteriously invisible bee, which derailed his glorious ride, slowing him inopportunely.

We all went for a hike around the oddly shallow and clear cypress pond, returning to the camp in time for an afternoon nap. Michael and Robby went trail riding while the rest of us dozed in the mild November sun and Sam-Ellen went for beer and such.

Our firewood supplied was buoyed by the afternoon visit of a firewood salesman, which allowed for a brief conversation between him and J. Michael on the merits and expense of woodcutters, and the virtue in the good hard work of chopping wood.

That evening was a low-key affair of similar events and fare, but the night grew colder than the night before, reaching the 40s. Jennifer and I froze, literally (ok, figuratively, but it sucked bad).

The night was riven by coyote calls and the cries of a nearby peacock, or a woman being murdered (we’ll never know).

At one point Robby got up to relieve himself and I called out in desperation for an extra blanket, which Robby graciously brought me in the dark cold night. Eventually Jennifer and I climbed into the tent, which was a bit warmer, if uncushioned. We only got to sleep for a couple of hours as a rooster crowed from an area farm.

With a loose deadline to return our borrowed cots and needing to get home in time to drive back to the park and then to the navy base, we woke up and got moving early, eating then packing. The camp eventually all woke in time to eat and hit the road right at 10 as planned. That is, until J. Michael, he of flat tire fame, got to work. He inflated his tires and leaned the bike against a tree while he packed, when out of the blue the tire burst and deflated in a flash. Cue Michael’s patch skills, which were unfortunately unable to correct the sidewall blowout, which was severe. Michael refused to use the brand new tube he’d found, dropped by an Ironman competitor, so he tried and tried to patch the tube until finally he relented, taking a spare tube to ride home on.

So, an hour later we finally departed, with Katie taking half the camp supplies in Robby’s car. Before we left, Sam re-wrapped his seat in towels. His poor posterior was not yet healed nor hardened for another Brooks ride, yet.

As we headed south on 79, taking a different course for fun and sights, we spotted a water bottle, which Robby scooped up. Shortly, we spotted another, and another. Then a gear bag with a multi tool, then a trip computer, spare tubes, and more! The trip home had become a giant scavenger hunt, as we rode what had been the final stretch on the Ironman, where competitors, tired, clumsy, or fed up, had ditched gear. Soon, we were all spotting stuff and calling it out, eventually gathering hundreds of dollars of gear. Our tired, under slept bodies were enlivened by the thrill of the hunt, and soon we had reached the mid-bay bridge and were topping it and rolling down towards the beach.

At the intersection of Gayle’s Trails and 79 we turned onto the trails, heading east. At Frank Brown Park, Jennifer and I continued east while Robby, J. Michael, Sam, and Mary-Ellen continued south to Diego’s for lunch and some beach time.

And with happy hearts and full packs, we went our separate ways, concluding another awesome ride. 10/10 would bike glamp again.

After the buffet dinner, we headed to the night show Ka Breath of Life. The fire live show was fantastic, however you had to deal with high humidity, lack of fresh air, and the worse was mosquitos bites. No prepared for such annoying, I'd used sunblock cream to sooth the itches and surprisingly it worked. I guessed the cream acted as a skin barrier or as the insect repellent. The bus took us back to the hotel past midnight.

I'm afraid it's not just in Britain that we get Saturdays when we don't want to venture out. I think it's even worse when you've just returned from holiday with dark rich tan looking a bit freakish.

Who wants to help put on the sunblock?

Website: www.mikesmithwick.com/

hehehe

don't ask me what's on her face... that's after her friendly fight with Papi...

to all u pervs out there, that's sunblock on deo's face.

Who wants to help put on the sunblock?

A sunblock covered child's face imprinted on a glass door.

Young beautiful sexy tanned happy woman in bikini on sea beach

COP 15

it's too late to be a pessimist.

dec. 09

Saint Joseph, Missouri USA ~ Copyright 2011 Bob Travaglione ~ FoToEdge Images

A sea of beach umbrellas.

www.youtube.com/watch?v=qjK04wdFzkU

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter .

Shau Kei Wan, Hong Kong

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Co art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter nservation Project, Maramba River Lodge, South Africa, Krugger National Park.

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

My face in Ultraviolet photography

Foto correspondente (correspondent photo): farm6.staticflickr.com/5067/5781288442_fe03428087.jpg

Explicação: A coloração escura da pele revela como a melanina que está presente em nosso corpo absorve a luz UV. É uma proteção natural. PS: Use SEMPRE protetor solar!!!

Explanation: About the dark skin: We can see the action of melanin in skin. This absorbs UV light, under these circumstances is a natural protection. PS: Use ALWAYS sunblock!!!

Câmera Sony: NEX-5N

filtro: Baader U

Exposição: 1/40sec.

Lente: Steinheil E Cassarit 50mm (M39)

Abertura: f/4

ISO: 800

Compensação de exposição: 0 EV

Weather: good weather (Tempo: tempo bom)

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter

Hippopotamuses love water, which is why the Greeks named them the "river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to keep their massive bodies cool under the hot African sun. Hippos are graceful in water, good swimmers, and can hold their breath underwater for up to five minutes. However, they are often large enough to simply walk or stand on the lake floor, or lie in the shallows. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. Hippos also bask on the shoreline and secrete an oily red substance, which gave rise to the myth that they sweat blood. The liquid is actually a skin moistener and sunblock that may also provide protection against germs. At sunset, hippopotamuses leave the water and travel overland to graze. They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to consume some 80 pounds (35 kilograms) of grass. Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water—they can match a human's speed for short distances. Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can suckle on land or underwater by closing their ears and nostrils. Each female has only one calf every two years. Soon after birth, mother and young join schools that provide some protection against crocodiles, lions, and hyenas. Hippos once had a broader distribution but now live in eastern central and southern sub-Saharan Africa, where their populations are in decline. A partially submerged hippopotamus tries to keep cool in the hot African sun. The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds and despite its stocky shape and short legs, it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[13][15] This hypothesized ancestral group likely split into two branches around 54 million years ago.[12] One branch would evolve into cetaceans, possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[17] The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[15]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[18] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos. Their common ancestor would have lived in the Miocene, about 20 million years ago. Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe, no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[19]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus.[18][19]

[edit]Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[20] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction.[20] Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[21]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene.[22] Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene. Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man. Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river. Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[9]:3 A hippo's lifespan is typically 40–50 years.[6]:277 Donna the Hippo, 60, was the oldest living hippo in captivity. She lived at the Mesker Park Zoo in Evansville, Indiana, USA[24][25] until her death on August 1, 2012. The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61.[26]

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[9]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) with a few exceptional specimens exceeding 3,600 kg (7,900 lb).[27][28] The heaviest known hippopotamus weighed approximately 4,500 kg (9,900 lb).[29] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25.[30]

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[31][32] The range of hippopotamus sizes overlaps with the range of the white rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[6]:260 The skin is 6 in (15 cm) thick,[33] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink.[6]:260 The testes of the males descend only partially and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female are unusual in that the vagina is ridged and two large diverticula protrude from the vulval vestibule. The function of these is unknown.[9]:28–29

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[6]:259 The jaw hinge is located far back enough to allow the animal to open its mouth at almost 180°.[9]:17 On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[34] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in).[33]

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[36] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region during antiquity but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome;[37] the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania and Kenya, north through to Ethiopia, Somalia and Sudan, west from Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia, Mozambique). Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water.[10] Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations.[1]

The hippo population declined most dramatically in the Democratic Republic of the Congo.[38] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[39] The decline is attributed to the disruptions caused by the Second Congo War.[39] The poachers are believed to be former Hutu rebels, poorly paid Congolese soldiers, and local militia groups.[39] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[40] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans. They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[41] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") was killed by hunters under authorization of the local authorities.[42][43] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities. Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water. Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[44] Like almost any herbivore, they will consume many other plants if presented with them, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[45] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[46] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress.[9]:84

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[45] Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[47]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes.[9]:4 The process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges into the water. As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food.[ Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[49] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown.[9]:49

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[9]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by gender. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[9]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond.[ Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[51] Males reach maturity at around 7.5 years. A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[9]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months.[51]

Mating occurs in the water with the female submerged for most of the encounter,[9]:63 her head emerging periodically to draw breath. Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a year.[9]:64 Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents. Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[53] Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation.[54] They are widely considered to be one of the most dangerous large animals in Africa.[55][56]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[57] Likely for the same reason, hippos are retromingent – that is, they urinate backwards.[58] When in combat, male hippos use their incisors to block each others attacks, and their lower canines to inflict damage.[6]:260 Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrink, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[52] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior. The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[59] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer Mountains.[9]:1 The ancient Egyptians recognized the hippo as a ferocious denizen of the Nile.

The hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD).[37][60] Hippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.[citation needed]

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief Dinizulu, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [61]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus. Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[63] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivity. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[9]:129[63]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitats. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[64] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo. A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[66] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young.[67] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[68] The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so that it can be inspected for fish bones.[70] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water.[70]

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[63] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[71] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandise, and many a stuffed hippo toy.[72][73] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[74] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[38] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the Animaniacs, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.[citation needed]

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [77] based in Munich, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos[contradiction] but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each time.[citation needed] The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.C. Botswana, Moremi National Park, Moremi Game reserve, private Reserve, Farm, chobe National park, Chobe Game Reserve, Zambia, Zambezi River, Livingstone, Zimbabwe, Kenya, Tanzania, Wildlife Conservation Project, Maramba River Lodge, South Africa, Krugger National Park. art beach blue bw california canada canon china city concert de england europe family festival film flower flowers food france friends green instagramapp iphoneography italy japan live london music nature new newyork night nikon nyc paris park party people photography portrait red sky snow square squareformat street summer sunset travel trip uk usa vacation water wedding white winter