Last updated on April 24, 2014 at 1:21 EDT

Northern River Otter

The Northern River Otter, Lontra canadensis, is a North American member of the Mustelidae or weasel family. It is also known as the North American River Otter. This species can be found all across North America, inhabiting inland waterways and coastal areas. It is found in Canada, Alaska, the Pacific Northwest, the Atlantic states, and the Gulf of Mexico.


They have streamlined, muscular bodies with short legs, webbed toes and a long muscular tail. The North American river otter’s body measure is somewhere between 25.98 to 42.13 in, and their tail measure is between 12.40 and 18.11 inches (a river otter’s tail makes up 30 to 40% of the total length of its body). It can weigh between 6 and 31 pounds. River otters have a round and small head and eyes, short yet powerful legs, and have large whiskers. Otters have sexual dimorphism, as the male is larger than the female. They have glossy dark brown fur and their throat is often silver grey. Otters are powerful swimmers, but can also travel quickly on land and often propel themselves into a rapid slide on their bellies on snow or ice. They also like to slide down riverbanks into the water. North American river otters have nostrils that close underwater and their fur is soft and dense. Both of these adaptations help them to live underwater. On land, the river otters can run up to 18 miles per hour. Their current life span is 10 to 15 years in the wild, but they can live up to 25 years in captivity.


Northern river otters have their dens on land. They hunt in a wide variety of aquatic habitats, including lakes, rivers, inland wetlands and swamps, coastal marshes and even the open ocean. In many areas of the United States and Canada, the damming activities of the beaver creates ideal habitat for otters.

Diet and natural history

Otters mainly eat fish but also eat insects, frogs, crustaceans and sometimes-small mammals. On occasion some larger river otters will attack and kill water birds such as ducks, geese, and even herons. They are capable of swimming in circles, which creates a whirlpool-like motion that brings fish from the bottom of the water up to the top. They are generally more active at night, dusk and dawn, but are active during the day where undisturbed by human activity. They use musk and urine to mark the land bordering their territories. They often use dens built by other animals, sometimes killing beavers or muskrats to take over their lodges. Females evict males while babies are still young, the male will return later however to help care for them when half-grown. North American river otters usually mate once a year in late winter or usually early spring. Males often mate with several females during the breeding season. They have a pregnancy period of 2 months, and the pups are weaned for 3 months. The size of the litter can range from 1 to 6 pups, but usually there are only 2 to 3. There is a delay in the implantation of the fertilized egg, so that the young are born in late winter or early spring. Mating occurs in water.


Like their relatives, the weasels, river otters are highly active predators. If an otter is not sleeping, it’s moving. They are very playful, chasing, sliding, swimming, jumping, and wrestling. This makes them popular for exhibits. However, they are not friendly towards humans if raised in captivity. Usually a captive raised river otter becomes very aggressive towards humans when it reaches sexual maturity, and thus they do not make good pets. There are times when otters have remained tame through their adult life, or have been taken from the wild as adults. However, “tame” is a relative term, even the most human-friendly otter will still bite and scratch, sometimes quite badly. They can be highly curious animals and have been known to follow trout fisherman along the opposite bank.

PHOTO CREDIT: Dmitry Azovtsev

Northern River Otter