Otters are semi-aquatic (or in one case aquatic) fish-eating mammals. The otter subfamily Lutrinae forms part of the family Mustelidae, which also includes weasels, polecats, badgers, as well as others. With thirteen species in seven genera, otters have an almost worldwide distribution. They mainly eat aquatic animals, predominantly fish and shellfish, but also other invertebrates, amphibians, birds and small mammals. The word otter derives from the Old English word otor or oter. This and cognate words in other Indo-European languages ultimately stem from a root which also gave rise to the English words water.[1] An otter's den is called a holt or couch. A male otter is a dog (otter), a female a bitch (otter), and a baby a whelp or pup. The collective nouns for otters are bevy, family, lodge or romp, being descriptive of their often playful nature, or when in water raft. Otters have long, slim bodies and relatively short limbs, with webbed paws. Most have sharp claws on their feet, and all except the sea otter have long muscular tails. They have a very soft, insulated underfur which is protected by their outer layer of long guard hair. This traps a layer of air, and keeps them dry and warm under water. Many otters live in cold waters and have very high metabolic rates to help keep them warm. Eurasian otters must eat 15% of their body-weight a day, and sea otters 20 to 25%, depending on the temperature. In water as warm as 10°C (50°F) an otter needs to catch 100 grams (3 oz) of fish per hour to survive. Most species hunt for 3 to 5 hours a day, and nursing mothers up to 8 hours a day. For most otters, fish is the primary staple of their diet. This is often supplemented by frogs, crayfish and crabs.[2] Some otters are expert at opening shellfish, and others will feed on available small mammals or birds. Prey-dependence leaves otters very vulnerable to prey depletion. Otters are very active, chasing prey in the water or searching the beds of rivers, lakes or the seas. Most species live beside water, entering it mainly to hunt or travel, otherwise spending much of their time on land to avoid their fur becoming waterlogged. The sea otter does live in the sea for most of its life. Otters are playful animals and appear to engage in various behaviors for sheer enjoyment. Different species vary in their social structure, with some being largely solitary, while others live in groups – in a few species these groups may be fairly large. Giant otter (Pteronura brasiliensis) Northern river otter (Lontra canadensis) Marine otter (Lontra felina) Southern river otter (Lontra provocax) Neotropical river otter (Lontra longicaudis) Sea otter (Enhydra lutris) Spotted-necked otter (Hydrictis maculicollis) Eurasian otter (Lutra lutra) Hairy-nosed otter (Lutra sumatrana) African clawless otter (Aonyx capensis) Oriental small-clawed otter (Aonyx cinerea) Smooth-coated otter (Lutrogale perspicillata) Genus Lutra Genus Hydrictis Genus Lutrogale Genus Lontra Genus Pteronura Genus Aonyx Genus Enhydra The northern river otter (Lontra canadensis) became one of the major animals hunted and trapped for fur in North America after European contact. River otters eat a variety of fish and shellfish, as well as small land mammals and birds. They grow to one metre (3 to 4 ft) in length and weigh from five to fifteen kilograms (10 to 30 lb). In some areas this is a protected species, and some places have otter sanctuaries, which help sick and injured otters to recover. Sea otters (Enhydra lutris) live along the Pacific coast of North America. Their historic range included shallow waters of the Bering Strait and Kamchatka, and as far south as Japan. Sea otters have some 200 thousand strands of hair per square centimetre of skin, a rich fur for which humans hunted them almost to extinction. By the time the 1911 Fur Seal Treaty gave them protection, so few sea otters remained that the fur trade had become unprofitable. Sea otters eat shellfish and other invertebrates (especially clams, abalone, and sea urchins), frequently using rocks as crude tools to smash open shells. They grow to 1.0 to 1.5 meters (2.5 to 5 ft) in length and weigh 30 kilograms (65 lb). Although once near extinction, they have begun to spread again, from remnant populations in California and Alaska. Unlike most marine mammals (such as seals or whales), sea otters do not have a layer of insulating blubber. As with other species of otter, they rely on a layer of air trapped in their fur, which they keep topped up by blowing into the fur from their mouths. They spend most of their time in the water, whereas other otters spend much of their time on land. This species (Lutra lutra) inhabits Europe, and its range also extends across most of Asia and parts of North Africa. In the British Isles they occurred commonly as recently as the 1950s, but became rare in many areas due to the use of chlorinated hydrocarbon pesticides and as a result of habitat-loss and water pollution (they remained relatively common in parts of Scotland and Ireland). Population levels attained a low point in the 1980s, but are now recovering strongly. The UK Biodiversity Action Plan envisages the re-establishment of otters by 2010 in all the UK rivers and coastal areas that they inhabited in 1960. Roadkill deaths have become one of the significant threats to the success of their re-establishment. The giant otter (Pteronura brasiliensis) inhabits South America, especially the Amazon river basin, but is becoming increasingly rare due to poaching, habitat loss, and the use of mercury and other toxins in illegal alluvial gold mining. This gregarious animal grows to a length of up to 1.8 metres (6 ft), and is more aquatic than most other otters. Norse mythology tells of the dwarf Ótr habitually taking the form of an otter. The myth of Otter's Ransom[5] is the starting point of the Volsunga saga. In some Native American cultures, otters are considered totem animals. The otter is held to be a clean animal belonging to Ahura Mazda in Zoroastrian belief, and taboo to kill.[6] Gavin Maxwell's book Ring of Bright Water tells the tale of how he brought a Smooth-coated Otter (Lutrogale perspicillata) back from Iraq and raised it in 'Camusfearna' (Sandaig), on the west coast of Scotland.[7] The Otter Pop is a frozen treat similar to a freezie. It features a cartoon otter on its package. The animated children's television show PB&J Otter featured a family of otters as the main characters. Russell, a sea otter and one of main characters from Happy Tree Friends. The character Hermione Granger has an otter-shaped patronus charm in the Harry Potter novels. In The Penguins of Madagascar, a character named Marlene is a smooth-coated or River otter and is voiced by Nicole Sullivan. The main character Tarka the Otter from the film and book of the same name is a European Otter. Some of the main characters in the Redwall series are otters. "Ray the Otter" is an Easter-egg found in the game Grand Theft Auto: Vice City Stories. "You can kill an Otter in about a second, just kick it's face off." Chris Morris in the satirical spoof documentary series Brass Eye Episode 1 - "Animals" Eurasian Otter Edinburgh Zoo Oriental small-clawed otter Long-tailed otter in Costa Rica Eurasian otter in holt otters at the Perth Zoo, Western Australia