Otter

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.

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.^{[citation needed]}

Characteristics

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. 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