Leatherback Turtle 2

Leatherback Sea Turtle (Dermochelys coriacea) at the National Museum of Natural History in Washington, DC on April-9th-2022.

It

is the largest of all living turtles and the heaviest non-crocodilian reptile, reaching lengths of up to 2 metres and weights of 600 kg.t is the only living species in the genus Dermochelys and family Dermochelyidae. It can easily be differentiated from other modern sea turtles by its lack of a bony shell; instead, its carapace is covered by oily flesh and flexible, leather-like skin, for which it is named.

 

Leatherback turtles have the most hydrodynamic body of any sea turtle, with a large, teardrop-shaped body. A large pair of front flippers powers the turtles through the water. Like other sea turtles, the leatherback has flattened forelimbs adapted for swimming in the open ocean. Claws are absent from both pairs of flippers. The leatherback's flippers are the largest in proportion to its body among extant sea turtles. Leatherback's front flippers can grow up to 2.7 m (8.9 ft) in large specimens, the largest flippers (even in comparison to its body) of any sea turtle.

 

The leatherback has several characteristics that distinguish it from other sea turtles. Its most notable feature is the lack of a bony carapace. Instead of scutes, it has thick, leathery skin with embedded minuscule osteoderms. Seven distinct ridges rise from the carapace, crossing from the cranial to caudal margin of the turtle's back. Leatherbacks are unique among reptiles in that their scales lack β-keratin. The entire turtle's dorsal surface is colored dark grey to black, with a scattering of white blotches and spots. Demonstrating countershading, the turtle's underside is lightly colored.[21] Instead of teeth, the leatherback turtle has points on the tomium of its upper lip, with backwards spines in its throat (esophagus) to help it swallow food and to stop its prey from escaping once caught.

 

 

Esophagus of a leatherback sea turtle showing spines to retain prey

D. coriacea adults average 1–1.75 m (3.3–5.7 ft) in curved carapace length (CCL), 1.83–2.2 m (6.0–7.2 ft) in total length, and 250 to 700 kg (550 to 1,540 lb) in weight.In the Caribbean, the mean size of adults was reported at 384 kg (847 lb) in weight and 1.55 m (5.1 ft) in CCL. Similarly, those nesting in French Guiana, weighed an average of 339.3 kg (748 lb) and measured 1.54 m (5.1 ft) in CCL.[24][25] The largest verified specimen ever found was discovered on the Pakistani beach of Sandspit and measured 213 cm (6.99 ft) in CCL and 650 kg (1,433 lb) in weight. A previous contender, the "Harlech turtle", was purportedly 256.5 cm (8.42 ft) in CCL and 916 kg (2,019 lb) in weight,however recent inspection of its remains housed at the National Museum Cardiff have found that its true CCL is closer to 1.5 m (4.9 ft), casting doubt on the accuracy of the claimed weight, as well. On the other hand, one scientific paper has claimed that the species can weigh up to 1,000 kg (2,200 lb) without providing more verifiable detail.The leatherback turtle is scarcely larger than any other sea turtle upon hatching, as they average 61.3 mm (2.41 in) in carapace length and weigh around 46 g (1.6 oz) when freshly hatched.

 

D. coriacea exhibits several anatomical characteristics believed to be associated with a life in cold waters, including an extensive covering of brown adipose tissue, temperature-independent swimming muscles,countercurrent heat exchangers between the large front flippers and the core body, and an extensive network of countercurrent heat exchangers surrounding the trachea.

 

 

Leatherbacks have been viewed as unique among extant reptiles for their ability to maintain high body temperatures using metabolically generated heat, or endothermy. Initial studies on their metabolic rates found leatherbacks had resting metabolisms around three times higher than expected for reptiles of their size. However, recent studies using reptile representatives encompassing all the size ranges leatherbacks pass through during ontogeny discovered the resting metabolic rate of a large D. coriacea is not significantly different from predicted results based on allometry.

 

Rather than using a high resting metabolism, leatherbacks appear to take advantage of a high activity rate. Studies on wild D. coriacea discovered individuals may spend as little as 0.1% of the day resting.This constant swimming creates muscle-derived heat. Coupled with their countercurrent heat exchangers, insulating fat covering, and large size, leatherbacks are able to maintain high temperature differentials compared to the surrounding water. Adult leatherbacks have been found with core body temperatures that were 18 °C (32 °F) above the water in which they were swimming.

 

Leatherback turtles are one of the deepest-diving marine animals. Individuals have been recorded diving to depths as great as 1,280 m (4,200 ft).[37][38] Typical dive durations are between 3 and 8 minutes, with dives of 30–70 minutes occurring infrequently.

 

They are also the fastest-moving non-avian reptiles. The 1992 edition of the Guinness Book of World Records lists the leatherback turtle moving at 35.28 km/h (21.92 mph) in the water. More typically, they swim at 1.80–10.08 km/h (1.12–6.26 mph

 

Leatherback sea turtles can be found primarily in the open ocean. Scientists tracked a leatherback turtle that swam from Jen Womom beach of Tambrauw Regency in West Papua of Indonesia to the U.S. in a 20,000 km (12,000 mi) foraging journey over a period of 647 days.[20][54] Leatherbacks follow their jellyfish prey throughout the day, resulting in turtles "preferring" deeper water in the daytime, and shallower water at night (when the jellyfish rise up the water column).[35] This hunting strategy often places turtles in very frigid waters. One individual was found actively hunting in waters where temperatures were as low as 0.4 °C (32.7 °F). Following each foraging dive, the leatherback would return to warmer (17.5 °C (63.5 °F)) surface waters to regain body heat before continuing to dive into near freezing waters.[55] Leatherback turtles are known to pursue prey deeper than 1000 m—beyond the physiological limits of all other diving tetrapods except for beaked whales and sperm whales.[56]

 

Their favored breeding beaches are mainland sites facing the deep water, and they seem to avoid those sites protected by coral reefs.[57]

 

Adult D. coriacea turtles subsist almost entirely on jellyfish.Due to their obligate feeding nature, leatherbacks help control jellyfish populations.[5] Leatherbacks also feed on other soft-bodied organisms, such as tunicates and cephalopods.

 

Pacific leatherbacks migrate about 6,000 mi (9,700 km) across the Pacific from their nesting sites in Indonesia to eat California jellyfish. One cause for their endangered state is plastic bags floating in the ocean. Pacific leatherback sea turtles mistake these plastic bags for jellyfish; an estimated one-third of adults have ingested plastic. Plastic enters the oceans along the west coast of urban areas, where leatherbacks forage, with Californians using upward of 19 billion plastic bags every year.

 

Several species of sea turtles commonly ingest plastic marine debris, and even small quantities of debris can kill sea turtles by obstructing their digestive tracts.Nutrient dilution, which occurs when plastics displace food in the gut, affects the nutrient gain and consequently the growth of sea turtles.[ Ingestion of marine debris and slowed nutrient gain leads to increased time for sexual maturation that may affect future reproductive behaviors.[63] These turtles have the highest risk of encountering and ingesting plastic bags offshore of San Francisco Bay, the Columbia River mouth, and Puget Sound.

 

 

The leatherback turtle is a species with a cosmopolitan global range. Of all the extant sea turtle species, D. coriacea has the widest distribution, reaching as far north as Alaska and Norway and as far south as Cape Agulhas in Africa and the southernmost tip of New Zealand.[20] The leatherback is found in all tropical and subtropical oceans, and its range extends well into the Arctic Circle.

 

The three major, genetically distinct populations occur in the Atlantic, eastern Pacific, and western Pacific Oceans.[ While nesting beaches have been identified in the region, leatherback populations in the Indian Ocean remain generally unassessed and unevaluated.

 

Recent estimates of global nesting populations are that 26,000 to 43,000 females nest annually, which is a dramatic decline from the 115,000 estimated in 1980.

 

Atlantic subpopulation

The leatherback turtle population in the Atlantic Ocean ranges across the entire region. They range as far north as the North Sea and to the Cape of Good Hope in the south. Unlike other sea turtles, leatherback feeding areas are in colder waters, where an abundance of their jellyfish prey is found, which broadens their range. However, only a few beaches on both sides of the Atlantic provide nesting sites.

 

Off the Atlantic coast of Canada, leatherback turtles feed in the Gulf of Saint Lawrence near Quebec and as far north as Newfoundland and Labrador.[47] The most significant Atlantic nesting sites are in Suriname, Guyana, French Guiana in South America, Antigua and Barbuda, and Trinidad and Tobago in the Caribbean, and Gabon in Central Africa. The beaches of Mayumba National Park in Mayumba, Gabon, host the largest nesting population on the African continent and possibly worldwide, with nearly 30,000 turtles visiting its beaches each year between October and April. Off the northeastern coast of the South American continent, a few select beaches between French Guiana and Suriname are primary nesting sites of several species of sea turtles, the majority being leatherbacks. A few hundred nest annually on the eastern coast of Florida.[6] In Costa Rica, the beaches of Gandoca and Parismina provide nesting grounds.

 

Pacific subpopulation

Pacific leatherbacks divide into two populations. One population nests on beaches in Papua, Indonesia, and the Solomon Islands, and forages across the Pacific in the Northern Hemisphere, along the coasts of California, Oregon, and Washington in North America. The eastern Pacific population forages in the Southern Hemisphere, in waters along the western coast of South America, nesting in Mexico, Panama, El Salvador, Nicaragua, and Costa Rica,as well as eastern Australia.

 

The continental United States offers two major Pacific leatherback feeding areas. One well-studied area is just off the northwestern coast near the mouth of the Columbia River. The other American area is located in California.[50] Further north, off the Pacific coast of Canada, leatherbacks visit the beaches of British Columbia.

 

Estimates by the WWF suggest only 2,300 adult females of the Pacific leatherback remain, making it the most endangered marine turtle subpopulation.

 

South China Sea subpopulation

A third possible Pacific subpopulation has been proposed, those that nest in Malaysia. This subpopulation, however, has effectively been eradicated. The beach of Rantau Abang in Terengganu, Malaysia, once had the largest nesting population in the world, hosting 10,000 nests per year. The major cause of the decline was egg consumption by humans. Conservation efforts initiated in the 1960s were ineffective because they involved excavating and incubating eggs at artificial sites which inadvertently exposed the eggs to high temperatures. It only became known in the 1980s that sea turtles undergo temperature-dependent sex determination; it is suspected that nearly all the artificially incubated hatchlings were female.[53] In 2008, two turtles nested at Rantau Abang, and unfortunately, the eggs were infertile. Additionally, there are small nesting sites in southern Thailand where 18 turtles nested in 2021

 

Indian Ocean subpopulation

While little research has been done on Dermochelys populations in the Indian Ocean, nesting populations are known from Sri Lanka and the Nicobar Islands. These turtles are proposed to form a separate, genetically distinct Indian Ocean subpopulation.[

 

 

Lifespan

Very little is known of the species' lifespan. Some reports claim "30 years or more", while others state "50 years or more".Upper estimates exceed 100 years.

 

Death and decomposition

Dead leatherbacks that wash ashore are microecosystems while decomposing. In 1996, a drowned carcass held sarcophagid and calliphorid flies after being picked open by a pair of Coragyps atratus vultures. Infestation by carrion-eating beetles of the families Scarabaeidae, Carabidae, and Tenebrionidae soon followed. After days of decomposition, beetles from the families Histeridae and Staphylinidae and anthomyiid flies invaded the corpse, as well. Organisms from more than a dozen families took part in consuming the carcass.

 

 

Leatherback turtles face many predators in their early lives. Eggs may be preyed on by a diversity of coastal predators, including ghost crabs, monitor lizards, raccoons, coatis, dogs, coyotes, genets, mongooses, and shorebirds ranging from small plovers to large gulls. Many of the same predators feed on baby turtles as they try to get to the ocean, as well as frigatebirds and varied raptors. Once in the ocean, young leatherbacks still face predation from cephalopods, requiem sharks, and various large fish. Despite their lack of a hard shell, the huge adults face fewer serious predators, though they are occasionally overwhelmed and preyed on by very large marine predators such as killer whales, great white sharks, and tiger sharks. Nesting females have been preyed upon by jaguars in the American tropics.

 

The adult leatherback has been observed aggressively defending itself at sea from predators. A medium-sized adult was observed chasing a shark that had attempted to bite it and then turned its aggression and attacked the boat containing the humans observing the prior interaction.Dermochelys juveniles spend more of their time in tropical waters than do adults.

 

Adults are prone to long-distance migration. Migration occurs between the cold waters where mature leatherbacks feed, to the tropical and subtropical beaches in the regions where they hatch. In the Atlantic, females tagged in French Guiana have been recaptured on the other side of the ocean in Morocco and Spain.

 

 

Mating takes place at sea. Males never leave the water once they enter it, unlike females, which nest on land. After encountering a female (which possibly exudes a pheromone to signal her reproductive status), the male uses head movements, nuzzling, biting, or flipper movements to determine her receptiveness. Males can mate every year but the females mate every two to three years. Fertilization is internal, and multiple males usually mate with a single female. This polyandry does not provide the offspring with any special advantages. Female leatherbacks are known to nest up to 10 times in a single nesting season giving them the shortest internesting interval of all sea turtles.

 

 

 

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