Euopean Otter
European otter at a glance
Size: Typically 60-90cm (2-3 ft.), with males larger than females; latter reaching only ~70cm. On average males ~70cm (2.3 ft.) and females 65cm. Tail 35-47cm (1.1-1.5 ft.), again longer in males than females. Stands ~30cm (12 in.) at shoulder and weighs 6-17kg (13-37 lbs.); typically ~9kg (20 lbs.) and 7kg (15.4 lbs.) for male and female, respectively. Possess a thick double-layered coat consisting of short (12mm / 0.5 in.) underfur that provides insulation and longer (25mm / 1 in.), coarse guard hairs for waterproofing. The coat is dense, with ~70,000 hairs/sq-cm (~455,000 sq-in.).
Colour/Appearance: A large semi-aquatic mustelid with long, thick tapering tail. Fur is typically dark brown, appearing almost black in some individuals when wet. They have a large brown/black nose, small eyes, small rounded ears that only just protrude beyond fur, and webbed feet. The head is broad and flat with long whiskers. Short legs give the typical low-slung mustelid appearance.
Distribution: Widespread throughout Britain, although patchily distributed in central and south-east England and parts of southern and central Scotland. Widespread in Ireland, rare on Isle of Wight, and absent from Isle of Man. More widely, found east through Russia into China, and south into north Africa and India.
Habitat: Typically a freshwater species inhabiting rivers, canals, marshes, and larger still water bodies (i.e., lakes, ponds and gravel pits) with sufficient cover. They may hunt or travel through ditches with only few centimetres of water. They will also hunt in urban areas with garden ponds, and on fishery sites. Occasionally found in seawater, particularly along rocky coastlines off Shetland and west coast of Scotland, although salt impairs their guard hair waterproofing and a source of freshwater is essential to ensure coat maintenance.
Longevity: Otters typically live 3-5 yrs, with the oldest wild specimen estimated at 16 yrs. In captivity, a female at Zürich Zoo lived to 18 yrs 2 months. Captive otters appear to show signs of senility at around 10 yrs old.
Sexing: With experience it is sometimes possible to sex mature specimens at distance (e.g., females have a smaller, thinner skull with less prominent forehead cf. males), but this is unreliable for animals less than 3 yrs old. The most reliable way is using the distance between the anus and penis/vulva, which is much larger in males. Males are referred to as dogs, females as bitches, and young are cubs.
Activity: Primarily nocturnal, although some local (e.g., urban and particularly coastal) populations are commonly active during the daytime. Perfectly adapted to water, swimming proficiently. Swims low in water with v-shaped bow wave, leaving a bubble trail while submerged. Otters can sustain swimming speeds of around 2 kmph (1.2 mph) for up to 8 hrs and dive for up to 45 seconds (possibly longer). Otters will travel across land, particularly when moving between ponds and dispersing, moving with a distinct humpback gait. they may sleep above ground in specially constructed "couches", or use dens constructed throughout their home range as "rest over" sites while travelling.
Territory/Home Range: Varies considerably with habitat from ca. 1 sq-km (250 acres) in productive marshland to 70 sq-km (43.5 mi.) of sparse riverbank in Shetland. Males range further than females; e.g., an average of ca. 39 km (24 mi.) vs. 20 km (12.4 mi.) of riverbank, respectively, in one study. Ranges of both sexes overlap. Journeys of 13 km (8.1 mi.) between watersheds have been recorded and radio-tracking suggests males are more likely to cover full extent of their territory, while females concentrate time in the most productive/secure area(s). Ranges are marked with droppings (called spraint), the frequency varying with the habitat quality, season, and (particularly) fish abundance.
An otter will create a den site called a holt, which is usually a cavity in riverbank, among tree roots, or in rocky crevice/cleft. Natural cavities appear selected where available, but animals may dig an extensive tunnel network (e.g., in peat). In urban areas, drain pipes and culverts may be used. Entrance to the holt may be underwater and chambers are often lined with leaves. Females appear more easily disturbed than males and may thus use more secure den sites. May create a "slide" outside the holt entrance, where vegetation worn away allowing easy/rapid access to the water.
Diet & Feeding: Otters are carnivorous, primarily piscivorous. Indeed, fish can account for 70-95% of diet, mostly relatively small, bottom-living species such as eels, perch, and salmonids. Carp may be locally important, which can put them in conflict with fisheries and amateur fish keepers alike. Crayfish and amphibians taken according to season and local abundance, while small water birds (e.g., up to about the size of a mallard) and mammals (e.g., water voles and rabbits) may also be predated, particularly in winter. Anecdotal reports of otters exiting rabbit warrens, and one report from South Uist of female otter with dependent cubs drowning a rabbit in a pool. Coastal otters take a wider variety of prey, including eelpout, rockling, butterfish, pollack, crabs, and octopus. May blow bubbles while hunting underwater to collect scent. Diet overlaps with American mink (Neovison vison) by ca. 70%. Males require ca. 12% body weight per day of food during winter.
Reproduction: Aseasonal breeders, with cubs reported in every month and no clear peak in births in most habitat, although there appears to be a strong tendency for May-August births in NW Scotland, Shetland, and the Netherlands. Courtship involves the pair chasing and playing for about a week, with copulation taking place in water. Typically 2-3 cubs are born, each about 13 cm (5 in.) long, following a gestation of ca. 62 days. Cubs are blind and furred at birth; eyes open around 30 days old and their first "enforced" swim is about 12 wks old, joining their mother on fishing trips by 4 months old. Cubs are weaned around 14 wks and independent at about 10 months old. Males mature at ca. 7.5 kg (16.5 lbs.) at 14 months old, and females slightly earlier at ca. 4.6 kg (10 lbs.) at about 10 months, although some reports pregnant animals as young as 8 months. Females produce a single litter per year and parental care is provided entirely by the female.
Euopean Otter
European otter at a glance
Size: Typically 60-90cm (2-3 ft.), with males larger than females; latter reaching only ~70cm. On average males ~70cm (2.3 ft.) and females 65cm. Tail 35-47cm (1.1-1.5 ft.), again longer in males than females. Stands ~30cm (12 in.) at shoulder and weighs 6-17kg (13-37 lbs.); typically ~9kg (20 lbs.) and 7kg (15.4 lbs.) for male and female, respectively. Possess a thick double-layered coat consisting of short (12mm / 0.5 in.) underfur that provides insulation and longer (25mm / 1 in.), coarse guard hairs for waterproofing. The coat is dense, with ~70,000 hairs/sq-cm (~455,000 sq-in.).
Colour/Appearance: A large semi-aquatic mustelid with long, thick tapering tail. Fur is typically dark brown, appearing almost black in some individuals when wet. They have a large brown/black nose, small eyes, small rounded ears that only just protrude beyond fur, and webbed feet. The head is broad and flat with long whiskers. Short legs give the typical low-slung mustelid appearance.
Distribution: Widespread throughout Britain, although patchily distributed in central and south-east England and parts of southern and central Scotland. Widespread in Ireland, rare on Isle of Wight, and absent from Isle of Man. More widely, found east through Russia into China, and south into north Africa and India.
Habitat: Typically a freshwater species inhabiting rivers, canals, marshes, and larger still water bodies (i.e., lakes, ponds and gravel pits) with sufficient cover. They may hunt or travel through ditches with only few centimetres of water. They will also hunt in urban areas with garden ponds, and on fishery sites. Occasionally found in seawater, particularly along rocky coastlines off Shetland and west coast of Scotland, although salt impairs their guard hair waterproofing and a source of freshwater is essential to ensure coat maintenance.
Longevity: Otters typically live 3-5 yrs, with the oldest wild specimen estimated at 16 yrs. In captivity, a female at Zürich Zoo lived to 18 yrs 2 months. Captive otters appear to show signs of senility at around 10 yrs old.
Sexing: With experience it is sometimes possible to sex mature specimens at distance (e.g., females have a smaller, thinner skull with less prominent forehead cf. males), but this is unreliable for animals less than 3 yrs old. The most reliable way is using the distance between the anus and penis/vulva, which is much larger in males. Males are referred to as dogs, females as bitches, and young are cubs.
Activity: Primarily nocturnal, although some local (e.g., urban and particularly coastal) populations are commonly active during the daytime. Perfectly adapted to water, swimming proficiently. Swims low in water with v-shaped bow wave, leaving a bubble trail while submerged. Otters can sustain swimming speeds of around 2 kmph (1.2 mph) for up to 8 hrs and dive for up to 45 seconds (possibly longer). Otters will travel across land, particularly when moving between ponds and dispersing, moving with a distinct humpback gait. they may sleep above ground in specially constructed "couches", or use dens constructed throughout their home range as "rest over" sites while travelling.
Territory/Home Range: Varies considerably with habitat from ca. 1 sq-km (250 acres) in productive marshland to 70 sq-km (43.5 mi.) of sparse riverbank in Shetland. Males range further than females; e.g., an average of ca. 39 km (24 mi.) vs. 20 km (12.4 mi.) of riverbank, respectively, in one study. Ranges of both sexes overlap. Journeys of 13 km (8.1 mi.) between watersheds have been recorded and radio-tracking suggests males are more likely to cover full extent of their territory, while females concentrate time in the most productive/secure area(s). Ranges are marked with droppings (called spraint), the frequency varying with the habitat quality, season, and (particularly) fish abundance.
An otter will create a den site called a holt, which is usually a cavity in riverbank, among tree roots, or in rocky crevice/cleft. Natural cavities appear selected where available, but animals may dig an extensive tunnel network (e.g., in peat). In urban areas, drain pipes and culverts may be used. Entrance to the holt may be underwater and chambers are often lined with leaves. Females appear more easily disturbed than males and may thus use more secure den sites. May create a "slide" outside the holt entrance, where vegetation worn away allowing easy/rapid access to the water.
Diet & Feeding: Otters are carnivorous, primarily piscivorous. Indeed, fish can account for 70-95% of diet, mostly relatively small, bottom-living species such as eels, perch, and salmonids. Carp may be locally important, which can put them in conflict with fisheries and amateur fish keepers alike. Crayfish and amphibians taken according to season and local abundance, while small water birds (e.g., up to about the size of a mallard) and mammals (e.g., water voles and rabbits) may also be predated, particularly in winter. Anecdotal reports of otters exiting rabbit warrens, and one report from South Uist of female otter with dependent cubs drowning a rabbit in a pool. Coastal otters take a wider variety of prey, including eelpout, rockling, butterfish, pollack, crabs, and octopus. May blow bubbles while hunting underwater to collect scent. Diet overlaps with American mink (Neovison vison) by ca. 70%. Males require ca. 12% body weight per day of food during winter.
Reproduction: Aseasonal breeders, with cubs reported in every month and no clear peak in births in most habitat, although there appears to be a strong tendency for May-August births in NW Scotland, Shetland, and the Netherlands. Courtship involves the pair chasing and playing for about a week, with copulation taking place in water. Typically 2-3 cubs are born, each about 13 cm (5 in.) long, following a gestation of ca. 62 days. Cubs are blind and furred at birth; eyes open around 30 days old and their first "enforced" swim is about 12 wks old, joining their mother on fishing trips by 4 months old. Cubs are weaned around 14 wks and independent at about 10 months old. Males mature at ca. 7.5 kg (16.5 lbs.) at 14 months old, and females slightly earlier at ca. 4.6 kg (10 lbs.) at about 10 months, although some reports pregnant animals as young as 8 months. Females produce a single litter per year and parental care is provided entirely by the female.