Otter

Otters are aquatic or marine carnivorous mammals, members of the large and diverse family Mustelidae, which also includes weasels, polecats, badgers, and others. There are 13 species of otter in 7 genera, with a distribution that is almost worldwide. more...

A group of otters is called a romp.

Physical characteristics

Otters have a dense layer (1,000 hairs/mm², 650,000 hairs per sq. in) of very soft underfur which, protected by their outer layer of long guard hairs, keeps them dry under water and traps a layer of air to keep them warm. Unlike most marine mammals (seals, for example, or whales), otters do not have a layer of insulating blubber.

All otters have long, slim, streamlined bodies of extraordinary grace and flexibility, and short limbs; in most cases the paws are webbed. Most have sharp claws to grasp prey but the short-clawed otter of southern Asia has just vestigial claws, and two closely related species of African otter have no claws at all: these species live in the often muddy rivers of Africa and Asia and locate their prey by touch.

Diet

Fish is the primary item in the diet of most otters, supplemented by frogs, crayfish, and crabs; some have become expert at opening shellfish, and others will take any small mammals or birds that happen to be available. To survive in the cold waters where many otters live, the specialised fur is not enough: otters have very high metabolic rates and burn up energy at a profligate pace: Eurasian otters, for example, must eat 15% of their body weight a day; sea otters, 20 to 25%, depending on the temperature. In consequence, otters are very vulnerable to prey depletion. In water as warm as 10°C an otter needs to catch 100 g of fish per hour: less than that and it cannot survive. Most species hunt for 3 to 5 hours a day, nursing mothers up to 8 hours a day.

Species

Northern River Otter

The northern river otter (Lontra canadensis) was one of the major animals hunted and trapped for fur in North America after contact with Europeans. They are one of the most playful and active, making them a popular exhibit in zoos and aquaria, but unwelcome on agricultural land because they alter river banks for access, sliding, and defense. River otters eat a variety of fish and shellfish, as well as small land mammals and birds. They are 1 m (3 to 4 feet) in length and weigh from 5 to 15 kg (10 to 30 pounds). They were once found all over North America, but are rare or extinct in most places, although flourishing in some locations.

Otters are a protected species in some areas and some places have otter sanctuaries. These sanctuaries help ill and injured otters to recover.

Sea Otter

The sea otter Enhydra lutris is found 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 200,000 hairs per square cm of skin, a rich fur for which they were hunted almost to extinction. By the time they were protected under the 1911 Fur Seal Treaty, there were so few sea otters left that the fur trade had become unprofitable.

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