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Who Are Otters?

River otters are highly social members of the weasel family that are well adapted to living in water. They are mammals in the Carnivora order who belong to the Mustelidae family. The Mustelidae family, or weasel family, contains about 70 different species of animals that are generally characterized by their round ears, short legs, small bodies, and thick fur. River otters belong to the Lontra genus which is the genus of otters from the Americas. The species name of the river otter is the Lontra canadensis, where canadensis means “of Canada.”

How Are River Otters Classified?

Class: Mammalia
Order: Carnivora
Family: Mustelidae
Genus: Lontra
Species: canadensis

What Do They Look Like?

The river otter is a small, furry animal with short, powerful legs and a long, slender body. On average, males weigh 25 pounds and are about five percent larger than females, who usually weigh only 19 pounds. Since the males are larger than the females, this makes them sexually dimorphic. Body length ranges from 26 inches to 42 inches, but about a third of the total body length is its long, tapered tail.

A river otter’s tapered tail is flexible and muscular, and helps the otter swim and stay balanced. Its body is streamlined, limber, and designed for life in the water. This animal is usually various shades of brown, with darker fur on its back and lighter fur on its sides and stomach. Its neck and head are the same diameter and they have short, rounded ears, fully webbed toes, and thick fur. This animal is usually various shades of brown, with darker fur on its back and lighter fur on its sides and stomach.

What Are Their Senses Like?

River otters have a very sharp sense of smell, hearing, sight, and touch. An otter’s sense of smell is very important because it helps it locate food, search for and identify other otters, find its home, and detect danger. Its sharp sense of hearing is even more important than its sense of smell, when it comes to detecting danger on land. River otters rely on their eyesight to find food. They have a specialized lens and cornea that correct for the refraction of light caused by the change from above and below the water. For this reason, their vision underwater is just as clear as it is above water! An otter uses its sense of touch to forage for food in mud or from underneath rocks. Its vibrissae, or whiskers, also play a huge role in finding prey because they are very sensitive to changes in the water, such as vibrations.

What Kind of Tracks Do They Make?

River otter tracks show five pointed toes around a small heel pad and are about 3 to 3 ½ inches wide and 3 to 4 inches long. Tracks can be found in soft mud, damp sand, or fresh snow. When a river otter travels by land, it normally walks, runs, or jumps. Otters normally make trails along the edges of rivers, lakes, streams, and other waterways. Trails are about 6 to 7 inches wide and normally lead to slides, dens, or coves.

For more information, see the References and Further Reading page.