Classification

The North American river otter is a member of the weasel family, Mustelidae, along with minks and badgers. Class: Mammalia Order: Carnivora Family: Mustelidae

Genus: Lontra Species: canadensis

Distribution

North American river otters are rare throughout most of their former range. They are still found in Alaska and most of Canada, in the Pacific Northwest, the Great Lakes states and along the Atlantic Coast and Gulf of Mexico. Now that rivers and streams have been cleaned up, several states, including Colorado, are reintroducing otters to their former habitat.

Habitat

River otters live in estuaries, fresh water lakes, streams, rivers and coastal areas. As long as there is unpolluted water and an adequate supply of food nearby, they can be found in prairie, tundra and high mountain ecosystems.

Physical Description

• River otters are three to four feet (0.9-1.2 m) long from nose to tail.
• Weight is 15-30 pounds (7-14 kg); males are larger than females.
• Dense short brown fur with silver or grayish fur on their bellies, throat and cheeks.
• They have long streamlined bodies, thick tapered tails and short legs. Their feet have claws and are completely webbed.

Diet

What Does It Eat?

In the wild: fish, crayfish, eels, turtles, snails, water insects, amphibians, birds, eggs, small mammals and occasionally aquatic plants. At the zoo: commercially prepared meat, fish and dog chow. They get live prey for behavioral enrichment.

What Eats It?

Otters are sometimes subject to predation by bobcats, wolves, coyotes, birds of prey, alligators and other large predators.

Social Organization

Otters are solitary except for mating pairs and females with young. They are slightly territorial and practice mutual avoidance rather than fighting over territory.

Life Cycle

Otters are mature at about two years. Mating occurs in late winter or early spring. Although gestation only lasts two months, the young may be born up to a year after mating since otters exhibit delayed implantation. Litters of one to six kits are usually born in the spring when the weather is warmer and food is plentiful. The young are born blind and helpless but fully furred with short whiskers and developed claws. They weigh about four ounces (112 gm) at birth and are about the size of a chipmunk. Their eyes open at about one month and they are weaned at about three months. The young begin venturing out of the den at about three months, when they start learning how to swim and how to catch prey from their mother. By six months they are full grown and proficient at hunting and swimming. They may stay with their mother until they are eight to 12 months old or until a new litter arrives. River otters live up to 15 years in the wild and up to 25 years in captivity.

Adaptations

Velvet Coat

The otter’s thick velvety fur is the most durable North American fur. They have a short thick undercoat for warmth and long outer guard hairs that are waterproof. They even have fur on the bottom of their feet that provides warmth as well as traction on snow and ice.

Curb Feelers

Otters have long, stiff whiskers called vibrissae that are used to detect moving prey and help the otters avoid obstacles in dark or murky rivers and lakes. While underwater an otter’s smell, vision and hearing are diminished so the sensitive vibrissae are an important sensory adaptation used in hunting. Other adaptations for a semi-aquatic lifestyle include a streamlined body, webbed feet and waterproof fur. Their ears and nose have valve-like skin flaps that close underwater. They have a special lens on their eyes to help them see underwater. Their flexible bodies can make quick turns underwater to keep up with prey.

Tag—You’re It!

Otters play more than most wild animals. They have been observed wrestling, chasing other otters, diving for rocks and clamshells, swimming with pebbles or other small objects balanced on their noses, toying with live prey and sliding down mud banks or snow banks. “Play” activities actually serve a purpose – they are used to strengthen social bonds, practice hunting techniques and scent—mark territories. Additionally, sliding down a bank is a fast, energy conserving way to cover a distance quickly!

Conservation Connection

IUCN Status: Least Concern.

River otter numbers declined due to habitat loss, water pollution, pesticide use, trapping for their luxurious fur and hunting by humans who thought otters were competing with commercial or sport fishing. Because of nationwide efforts to clean up pollution in rivers, streams and lakes, several states, including Colorado, have been able to reintroduce river otters to their former habitat.

Fun Facts

• Otters have the densest fur of any mammal with up to 850,000 hairs per square inch.
• River otter mothers catch and release prey to help to teach young otters how to forage and catch food items.
• They can swim an average speed of seven miles per hour, run on land at a speed of 15-18 miles per hour and stay underwater for up to eight minutes! • River otters are the only truly amphibious members of the weasel family.