Otter Research

Lontra canadensis
northern river otter

North American river otters occur throughout Canada and the United States, except for areas of southern California, New Mexico, and Texas, and the Mohave desert of Nevada and Colorado. In Mexico they are found in the delta areas of the Rio Grande and Colorado river. Otters were locally extirpated from portions of their range but reintroduction and conservation efforts have helped stabilize populations.

North American river otters are found anywhere there is a permanent food supply and easy access to water. They can live in freshwater and coastal marine habitats, including rivers, lakes, marshes, swamps, and estuaries. River otters can tolerate a variety of environments, including cold and warmer latitudes and high elevations. North American river otters seem to be sensitive to pollution and disappear from areas with polluted waters.

North American river otters build dens in the burrows of other mammals, in natural hollows, such as under a log, or in river banks. Dens have underwater entrances and a tunnel leading to a nest chamber that is lined with leaves, grass, moss, bark, and hair.

North American river otters are semi-aquatic mammals, with long, streamlined bodies, thick tapered tails, and short legs. They have wide, rounded heads, small ears, and nostrils that can be closed underwater. The vibrissae are long and thick, reflecting their importance in sensory perception. The fur is dark brown to almost black above and a lighter color ventrally. The throat and cheeks are usually a golden brown. The fur is dense and soft, effectively insulating these animals in water. The feet have claws and are completely webbed. Body length ranges from 889 to 1300 mm and tail length from 300 to 507 mm. Weight ranges from 5 to 14 kg. Males average larger than females in all measurements.

North American river otters eat mainly aquatic organisms such as amphibians, fish, turtles, crayfish, crabs, and other invertebrates. Birds, their eggs, and small terrestrial mammals are also eaten on occasion. They sometimes eat aquatic plants.
Prey is captured with the mouth, and mainly slow, non-game fish species are taken, e.g., suckers. The otter's long whiskers are used to detect organisms in the substrate and the dark water. Prey is eaten immediately after capture, usually in the water, although larger prey is eaten on land.

North American river otters are important parts of healthy, aquatic ecosystems.

North American river otters have been hunted for many years for their attractive and durable fur. In the 1983-84 hunting season, 33,135 otters were taken with an average selling price of $18.71 per pelt. Otters are stll an important source of income for many people in Canada and the western United States. River otters also eat "trash fish" that compete with more economically desirable game fish.

Northern river otters are listed in Appendix II of CITES. Populations were once extirpated through many parts of their range, especially around heavily populated areas in the midwestern and eastern United States. Population trends have stabilized in recent years and reintroduction and conservation efforts have resulted in recolonization of areas where they were previously extirpated. Northern river otter populations are still considered vulnerable or imperiled throughout much of their range in midwestern United States and the Appalachian mountains. They are presumed extirpated in New Mexico and population status in South Carolina and Florida has not yet been reviewed.

Members of the weasel family, playful river otters enjoy sliding down muddy and snowy hills, bouncing objects on their paws, playing tag, and wrestling.

Description
Built for swimming, river otters have a streamlined body, short legs with webbed feet, dense fur that keeps otters warm, a tapered tail, small ears, and nostrils that can close underwater. They can grow to be more than a meter long, from head to tail, and weight up to 14 kg.

Range 
Once abundant in U.S. and Canadian rivers, lakes, and coastal areas, river otters have suffered from fur trapping, water pollution, habitat destruction, pesticides, and other threats. Today, they can be found in parts of Canada, the Northwest, upper Great Lakes area, New England, and Atlantic and Gulf Coast states

Habitat
River otters can make themselves at home in nearly any inland waterway, as well as estuaries and marine coves.
Diet
These otters eat fish, frogs, crayfish, mollusks, other invertebrates, and small mammals.

Behavior
Male and female otters are generally solitary, except when adult females care for their juvenile offspring, who disperse by the time the otters give birth again.

At the Zoo 
North American river otters can be seen in the Zoo's Beaver Valley. Their cousins, Asian small-clawed otters, can be seen on Asia Trail.

Fun Facts
The largest of the 13 species of otter is the giant otter, reaching a length of up to 1.8 m and known as the river wolf in Peru. The smallest is the Asian small-clawed otter, less than a meter long.
North American river otters can dive to a depth of 60 feet.

National Zoo
Animal Diversity