Otter, a mammal that lives in and near water. Otters are related to weasels, badgers, and skunks. They are noted for their playfulness and swimming ability, if caught young, members of most species make intelligent pets. Otters are found throughout most of the world. Two species live in North America—the river otter (also called the common, land, or Canadian otter) and the sea otter.

The sea otterThe sea otter swims and floats on its back.

The river otter lives in and near freshwater throughout North America north of Mexico. It weighs 10 to 30 pounds (4.5 to 13.5 kg) and is from 35 to 54 inches (90 to 140 cm) long including the 18-inch (45-cm) tail. A river otter has a blunt head, a thick neck, and a roughly tubular body that narrows to a heavy, tapered tail. Its streamlined body, short legs, and webbed feet make it an excellent swimmer Its brown coat is thick and smooth, and makes durable fur.

River otters build dens with underwater entrances in the banks of streams or lakes. They spend most of their time in water, and when diving are able to close their nostrils and ears. They are most active at night River otters eat mainly crayfish, frogs, turtles, and fish. They have one to four pups each year. The pups must be taught to swim and do not leave their mothers until they are about one year old. Both adults and young spend hours sliding down river or snow banks into the water.

Sea otters live in groups in shallow kelp beds among the Aleutian Islands and on the Pacific coast as far south as southern California. They are larger than river otters. The male weighs up to 80 pounds (36 kg) and is about four feet (1.2 m) long; the female is somewhat smaller. The sea otter's tail is shorter than that of the river otter, but its hind feet are larger and are flattened into broad flippers. The sea otter swims and floats on its back. It places a rock on its chest and uses it as an anvil for breaking open shellfish, its chief food. Sea otters do not have a layer of blubber for insulation, but air trapped in the long, soft fibers of hair keeps them warm.

Sea otters, once hunted to near extinction for their highly prized darkish brown fur, are protected by international law. However, due to water pollution and destruction of habitat sea otters are still threatened with extinction.

Which Mustelid Floats Around on Its Back?

Sea otters live in the North Pacific Ocean, off the west coast of North America and the east coast of Siberia. These animals float around on their back, using their webbed back feet to paddle about in the sea. When napping, sea otters often wrap themselves in kelp (a kind of seaweed) to prevent drifting during their sleep. When hungry, they dive to the ocean floor to get their food. They can stay underwater for up to four minutes.

Sea otters spend almost their whole life at sea. They come ashore only rarely, to rest on rocks. They eat, sleep, and raise their young in the water.

Keeping warm is important for mammals that live in the ocean. Other mammals that live in the ocean, such as seals, whales, and dolphins, have a layer of fat, called blubber, under their skin. Blubber keeps these animals warm and helps them stay afloat. Otters do not have blubber, but their thick fur holds a lot of air. This layer of air acts like blubber to help otters stay afloat and keep warm.

Why Does a Sea Otter Carry a Rock?

Sea otters eat seafood. Their diet includes fish, octopuses, and squids. But they also eat a lot of shellfish, including abalones, clams, crabs, sea snails, and mussels. Sea otters grab shellfish with their front paws rather than with their mouths.

To open the hard shell of a shellfish, a sea otter places a rock on its own chest. The sea otter then uses its paws to pound the shellfish on the rock. When the shell breaks open, the sea otter can eat the soft body of the shellfish. A sea otter also uses its large, flat back teeth to crush hard shells.

Otters belong to the family Mustelidae, subfamily Lutrinae. The river otter is Lutra canadensis; the sea otter, Enhydra lutris.