North American River Otter

Characteristics

North American River Otters have long, slender, and sleek bodies. Head is small and round, with small eyes and ears; prominent whiskers. Legs short, but powerful; all four feet webbed. Tail long and slightly tapered toward the tip with musk-producing glands underneath. The short dense fur is dark brown. Chin and stomach are reddish yellow, tinged with gray. Females are usually a third smaller than males.

Species Specifics

Unlike sea otters, river otters are smaller, swim on their bellies, sleep in underground dens, and eat their food on a log or rock, not on their bellies.

Physical Characteristics

American River Otters are almost impervious to cold because of an outer coat of coarse guard hairs, plus a dense, thick undercoat that helps to "water-proof" the animal. They have no blubber; it's the fur that keeps them warm. Perianal scent glands are used for identification, defense, marking territory, and trail marking. Small ears and nostrils can be tightly closed when in water; they are excellent swimmers and divers. During a dive, their pulse slows to a tenth of the normal rate of 170 beats a minute, thereby conserving oxygen

Ecology

Habitat

streams, rivers, lakes, estuaries, and salt- and freshwater marshes

Distribution

Diet

Fish, crawfish, frogs, turtles, and aquatic invertebrates, plus an occasional bird, rodent or rabbit. Because otters prey most easily on fish that are slow and lethargic, much of the diet consists of "rough" fish like carp, suckers, catfish, and sculpins.

Ecological Web

North American River Otters are important predators of fish and aquatic invertebrates.

Activity and Behavior

Activity Pattern

Behavior

Social Behavior

American River Otters live alone or in family groups, typically females and their young. They are known as playful animals, exhibiting behaviors such as mud or snow sliding, burrowing through the snow, and waterplay. Many "play" activities actually serve a purpose. Some are used to strengthen social bonds, to practice hunting techniques, and to scent mark. North American river otters get their boundless energy from their very high metabolism, which also requires them to eat a great deal during the day.They are excellent swimmers and divers, able to stay underwater for up to 8 minutes. They are also fast on land, capable of running at up to 29 km/hr. These otters normally hunt at night, but can be seen at all times of day. North American River Otters communicate using a variety of techniques. They vocalize with whistles, growls, chucles, and screams. They also use paired scent glands near the base of their tails for scent marking. They also urinate or defecate on vegetation within their home range to mark territory. They also use touch and posture as a means of communication.

Reproductive Behavior

The female mates in the spring shortly after giving birth to two to four young (or she might skip a year). The new litter of young will not begin to develop until late in the fall. This process, known as delayed implantation, enables the fertilized eggs to mark time within her, receiving only sparse ration to stay alive for several months. Then, within her body, a signal awakens the tiny embryos which resume their growth. The otter pups start their life in a burrow in a river bank, usually an abandoned muskrat den. Born blind and helpless, they are nursed by the female for a month. Venturing out of the den, they rough-house and play in the shallow water, where their mother teaches them to swim and hunt.

Offspring

2-4 offspring, open eyes at 1 month, weaned at 3 months, independent at 6-12 months

Conservation

Status

The North American River Otter is considered to be Least Concern as it is not currently declining at a rate sufficient for a threat category. By the early 1900s, river otters had declined throughout large portions of their historic range in North America. However, improvements in water quality (through enactment of clean water regulations) and furbearer management techniques have enabled river otters to reclaim portions of their range in many areas. Reintroduction projects have been valuable in restoring otter populations in many areas of the United States. However, river otters remain rare or absent in the southwestern United States and water quality and development limit recovery of populations in some areas.

Historical

Originally this species is thought to have ranged from 250-700°N latitude and from 530 to 1660°W longitude. Habitat loss and pollution caused reductions in range area and the species is now absent or rare in Arizona, Hawaii, Indiana, Iowa, Kansas, Kentucky, Nebraska, New Mexico, North Dakota, Ohio, Oklahoma, South Dakota, Tennessee, and West Virginia. Reintroductions have expanded the distribution of this species in recent years, especially in the Midwestern United States.

Current Threats

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