Otter Facts

River otters spend most of their lives on land close to a river or lakeshore. They build dens or take over dens abandoned by other animals, such as beavers or foxes.

River otters forage in the water for food such as fish. They usually take their food to shore instead of eating it in the water.

There are several species of river otter. The North American river otter, Lontra canadensis, generally weighs 20 to 25 pounds and has a long tail that's about half the length of its body. When they swim, river otters keep their bellies down and paddle with their webbed feet.

Sea otters are much larger than river otters, typically between 50 and 100 pounds. A sea otter's tail is flattened, and it's shorter than a river otter's. Sea otters spend almost all of their time in large bodies of saltwater, such as oceans, bays, and sounds, and they tend to be clumsy on land.

When a sea otter swims, it usually stays on its back and paddles with its tail and flippers. Unlike their river cousins, sea otters don't have much blubber and tend to have softer, thicker fur. Sea otters use rocks to crack open shells to get at their prey.

All otters are predators, so they help keep their ecosystems in balance by controlling prey populations. River otters sometimes feed on fish species that compete with fish that humans like to eat, so they help ensure bigger populations of commercially valuable species for fishermen. Sea otters often prey on sea urchins. An overabundance of sea urchins can kill off kelp, a plant that's necessary for many marine animals' survival.

Traditionally, otters were hunted or trapped for their pelts. Some populations, including sea otters, were driven nearly to extinction. The hunting and trapping of sea otters is now banned and the hunting of river otters has been highly restricted. Poachers are still a threat, however.

Habitat destruction is a more serious threat to otters. Wetland drainage and pollution have destroyed many traditional river otter habitats. And sea otters are threatened by oil spills and toxic materials. Fishing techniques that use large nets or traps pose a threat to sea otters because the animals can become caught and drown.