North American River Otter

The **North American river otter** (*Lontra canadensis*), also known as the **northern river otter** or **common otter**, is a semiaquatic mammal endemic to the North American continent found in and along its waterways and coasts. An adult North American river otter can weigh between 5.0 and 14 kg (11.0 and 30.9 lb). The river otter is protected and insulated by a thick, water-repellent coat of fur.

The North American river otter, a member of the subfamily Lutrinae in the weasel family (Mustelidae), is equally versatile in the water and on land. It establishes a burrow close to the water's edge in river, lake, swamp, coastal shoreline, tidal flat, or estuary ecosystems. The den typically has many tunnel openings, one of which generally allows the otter to enter and exit the body of water. Female North American river otters give birth in these burrows, producing litters of one to six young.

## Description

The playful North American river otter is well adapted for semi-aquatic living. The mammals have thick, protective fur to help them keep warm while swimming in cold waters. They have short legs, webbed feet for faster swimming, and a long, narrow body and flattened head for streamlined movement in the water. A long, strong tail helps propels the otter through the water. They can stay underwater for as many as eight minutes. North American river otters have long whiskers, which they use to detect prey in dark or cloudy water, and clawed feet for grasping onto slippery prey. They are very flexible and can make sharp, sudden turns that help them catch fish. Their fur is dark brown over much of the body, and lighter brown on the belly and face. On land a river otter can run at speeds of up to 15 miles (24 kilometers) an hour—they can slide even faster. Their playful snow and mud sliding, tail chasing, water play, and snow burrowing activities also serve other purposes—they help strengthen social bonds and let young otters practice hunting techniques.

A river otter can grow three to four feet (0.9 to 1.2 meters) long including its tail and weigh between 11 and 30 pounds (5 to 14 kilograms). Males are generally larger than females. The tail makes up about a third of their total length.

## Range

The North American river otter occurs in much of Canada and the United States, except for portions of the Southwest, and in Mexico in the Rio Grande and Colorado River delta areas. They can thrive in any water habitat, such as ponds, marshes, lakes, rivers, and estuaries—in cold, warm, or even high-elevation areas—as long as the habitat provides adequate food. River otter dens are along the water in abandoned burrows or empty hollows. The dens have entrances underwater so they can be easily accessed from the water. Bobcats, alligators, coyotes, raptors, and other large predators will sometimes prey on North American river otters.

## Diet

River otters eat a variety of aquatic wildlife, such as fish, crayfish, crabs, frogs, birds’ eggs, birds and reptiles such as turtles. They have also been known to eat aquatic plants and to prey on other small mammals, such as muskrats or rabbits. They have a very high metabolism, so they need to eat frequently.

## Behavior

North American river otters are active year-round, and are most active at night and during crepuscular hours. They become much more nocturnal in the spring, summer, and fall seasons, and more diurnal during winter. They may migrate as a result of food shortages or environmental conditions, but they do not migrate annually. North American river otters only settle in areas that consist of vegetation, rock piles, and sufficient coverage.

### **Playing**

North American river otters are renowned for their sense of play. Otter play mostly consists of wrestling with conspecifics. Chasing is also a common game. North American river otters rely upon play to learn survival skills such as fighting and hunting. However, playful behavior was found in only 6% of 294 observations in a study in Idaho, and was limited mostly to immature otters.

### **Social Behavior**

The North American river otter is more social than most mustelids. In all habitats, their basic social group is the family, consisting of an adult female and her progeny. Adult males also commonly establish enduring social groupings, some documented to comprise as many as 17 individuals. In coastal areas, males may remain gregarious even during the estrous period of females. Family groups may include helpers, which can be made up of unrelated adults, yearlings, or juveniles. Male North American river otters disperse from such family groups more often than females. When females leave, they tend to move much further away (60–90 km or 37–56 mi) than males (up to 30 km or 19 mi), which tend to move shorter distances. Male North American river otters do not seem to be territorial, and newly dispersing males may join established male groups. On occasion, groups of unrelated juveniles are observed. North American river otters living in groups hunt and travel together, use the same dens, resting sites, and latrines, and perform allogrooming. In freshwater systems, groups occur most often in autumn and during early winter. From mid-winter through the breeding season, adult females move and den alone. River otters are not territorial, but individual North American river otters of different groups portray mutual avoidance. Home ranges of males are larger than those of females, and both sexes exhibit intra- and intersexual overlap of their domains.

### **Communication**

Communication among North American river otters is accomplished mainly by olfactory and auditory signals. Scent marking is imperative for intergroup communication. The North American river otter scent-marks with feces, urine, and possibly anal sac secretions. Musk from the scent glands may also be secreted when otters are frightened or angry. North American river otters can produce a snarling growl or hissing bark when bothered, and a shrill whistle when in pain. When at play or traveling, they sometimes give off low, purring grunts. The alarm call, given when shocked or distressed by potential danger, is an explosive snort, made by expelling air through the nostrils. North American river otters also may use a birdlike chirp for communication over longer distances, but the most common sound heard among a group of otters is low-frequency chuckling.

## Life Histoy

River otters breed in late winter or early spring. Adults generally give birth to between one and three pups, which are blind and helpless when born. They first learn to swim after about two months. River otters generally live alone or in small social groups. They can live eight to nine years in the wild but have lived up to 21 years in captivity.

## Conservation

North American river otters were hunted and trapped extensively for their fur in the 19th and 20th centuries, and are still hunted in some places. They were extirpated from portions of their range, but conservation and reintroduction efforts are helping populations to recover. However habitat destruction and water pollution still puts these animals at great risk, especially because they are so specialized.

## Gallery

North American river otter eating a White Sucker Catfish (catostomus commersonii) at the Seedskadee National Wildlife Refuge (Wyoming)Little BearThe SimpsonsFantasia 2000 (1999)Zootopia (2016)