Northern Prairie Wildlife Research Center
Description: The river otter has a long cylindrical body. Its total length ranges from 35-54 inches (89-137 cm). It weighs 11-33 pounds (5-15 kg). The thick, tapering tail measures 1/3 of the body length. The river otter has webbed feet with 5 toes and nonretractable claws. It has a dark brown coat, with a silver-gray throat and white whiskers. Its pelt has short, dense underfur protected by longer, glossy guard hairs. Otter sign includes rolling areas of flattened vegetation, slides on river and snow banks and troughs in soft snow up to 1 foot wide.
Habitat and Habits: The river otter is found in rivers, ponds, lakes and unpolluted waters in wooded areas. Key habitat components are riparian vegetation, temporary den and resting sites (cavities under tree roots, shrub patches, tall grass) and adequate food. It is active all year, mainly at night. Air trapped in the fur insulates the river otter while underwater, where it can stay for up to 4 minutes. Long, stiff whiskers to locate prey and good underwater vision aid in hunting success.
The river otter is sexually mature at 2 years, breeding in early spring. The female has 2-3 pups (range 1-6) in a secluded natal den site. Young leave the den at 2 months, are weaned by 3 months, but remain with the female until just prior to the birth of the mother's next litter. It will occupy dens built by other animals, log jams and unused human structures.
River otters primarily eat fish. Other aquatic foods include frogs, crayfish and turtles, making the river otter a good barometer of water quality.
Distribution: The river otter is distributed throughout North America north of Mexico, except for extreme southwestem United States. In South Dakota, it has been reported from Hughes County along the Missouri River, with unverified reports from adjacent counties.
Conservation Measures: The river otter is affected by channelization of habitat and elimination of riparian woodlands. It is vulnerable to trapping and hunting. Reintroduction efforts have been successful in a number of states, returning this furbearer to much of its former range.