North American river otters are semi-aquatic mammals with long, streamlined bodies, short legs, and webbed feet. They have wide, rounded heads, small ears, and nostrils that can be closed tightly underwater. A long, rudder-shaped tail helps them turn quickly while swimming.

What They Eat
In the water, river otters hunt fish, crayfish, and amphibians. Their shape and flexibility make them fast swimmers. On land they can also catch chipmunks, mice, and young rabbits.

Where They Live
River otters spend equal time on land and in water. They live near rivers, lakes, marshes, swamps, and estuaries where they dig dens in river banks, under logs, or take over old beaver or muskrat lodges.

What They Do
Constant movement and soft, dense fur keep otters warm in Minnesota winters. When traveling on land, otters move along by flexing their spines inchworm-style. Always on the move, they may travel as far as 25 miles in a single week.

How They’re Doing
Although North American river otters are not considered endangered, their numbers have declined in many areas. A century ago otters became rare in Minnesota as their homes were drained and polluted. With recent conservation efforts, otters are coming back.

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North American River Otter

North American River Otter

North American River Otter

River otters can remain underwater for more than 4 minutes and dive to depths greater than 60 feet! They swim an average of 6 mph, and can sprint even faster for short distances by vertically flexing their bodies and tails back and forth along the surface of the water.

Oil and water don’t mix. Otters have glands under their tails that release oil used to waterproof their fur. To keep their oily coats clean and dry, otters must constantly groom themselves.

Air bubbles trapped between layers of fur helps otters stay warm in cold weather and cold water.

In murkey water, stiff whiskers act like anntenae and help otters detect moving prey and avoid obstacles.

At the Minnesota Zoo, North American river otters can be seen swimming and playing on the Minnesota Trail.  

Care at the Zoo

Enrichment is the process of creating an environment that addresses a zoo animal’s social, psychological, and physical needs. It increases activity, provides mental stimulation, and encourages animals to demonstrate their natural behaviors.

Otters are busy, playful animals and benefit from a variety of enrichment. Keepers occasionally offer the otters “popsicles” (specially made frozen treats that might include fish or meat), sometimes tossing them into the pool in their exhibit. Other enrichment items provided include pumpkins, pinecones, and antlers.

Your visit to the Zoo helps support our conservation programs. You can also sponsor an animal at the Zoo.

River otters have recently been added as a species managed under the Association of Zoos and Aquarium’s (AZA's) Otter Species Survival Plan (SSP). Because river otters are sensitive to habitat destruction and water pollution, they have been virtually eliminated throughout many parts of their original range, especially in the Midwest and East. They have been successfully reintroduced to many of these areas and are hopefully on a path to recovery.

Things the Zoo's Done/Doing

You can help protect the health of North American river otters by helping keep lakes, rivers, and wetlands clean! Keep litter, pet waste, and leaves out of street gutters and storm drains and dispose of household hazardous wastes properly. Chemicals poured down drains or tossed into the garbage can pollute local waterways.

River otters are high-energy animals, and constantly on the move. Because otters are so good at getting food, they have less need to compete and more time to play. Playful and gregarious, they spend a large part of their day wrestling with each other, sliding on their bellies, and playing chasing games. These largest members of the weasel family are excellent at catching fish, but spend equal time on land and in the water.

Range and Habitat
River otters prefer the freshwater of lakes, streams, rivers, and sloughs, but can also be found in the salt and brackish waters of coastal areas. They are sensitive to pollution and will disappear from areas where the water is contaminated. Formerly found across much of North America, their range has significantly decreased. Today, river otters are found in Canada, the East Coast and Great Lakes states, and as far south as Mexico. In Minnesota, river otters are found primarily in northern parts of the state.

Habits and Adaptations
These excellent swimmers and divers have an acute sense of touch, smell, and hearing. They are active day and night, but more so in the evening and early morning. They live in well-hidden dens in banks along the water’s edge. Their dens are lined with dry vegetation and have a main entrance that’s under water. Otters don’t migrate or hibernate. In the winter, they may combine running and sliding as a method of locomotion over snow and ice.

Diet
In contrast to sea otters, river otters eat on dry land. They prey on aquatic foods such as fish, crayfish, and amphibians. Occasionally, a small beaver or muskrat is also taken. When hunting fish, they seem to prefer suckers and non-game fish.

Social structure
River otters live in family groups. Both young and old are extremely playful and curious. They create mudslides and snow slides into lakes and ponds, and tunnel under the snow. Communication is done through scent marking and a variety of vocalizations including shrill whistles, chirps, snarls, growls, and hissing sounds. Female otters seem to be more aggressive than males in all situations.

Reproduction
Otters breed in late winter or early spring, usually mating in the water. After about 10 months, females give birth to a litter of 1 to 4 pups in March. Blind and toothless at birth, the pups are covered with short fur. They open their eyes 5-6 weeks later and remain in the nest 10-12 weeks before learning to swim and eat solid food. Pups are reluctant to enter the water and must be coaxed in and taught to swim by their mother. River otters are fully grown by one year and sexually mature by age two. Females are believed to exhibit delayed implantation of the egg (the fertilized egg after severing blastocyst ceases growth and lies inactive until implantation occurs).