River Otter

River Otter

Photo Credit: U.S. Fish and Wildlife Service

SCIENTIFIC NAME:  Lontra canadensis

DESCRIPTION:  The northern river otter (Lutra canadensis) is a member of the weasel family.  Adult body weights vary greatly, but normally range from 11 to 33 pounds.  Females are approximately one-third smaller than males.  Their ears are small and almost inconspicuous.  They have small heads that widen through the neck into a long, thickset but streamlined body. Their tails are muscular, dorsally flattened and tapered.  The tail makes up approximately 40 percent of the otter’s total length, which ranges from three to four-and-one-half feet.  They can drink while under water due to a special valve in their nose.  Otters have sharp claws and webbing between toes on all four feet. They have sharp canine teeth to catch and hold their prey.  The otter’s pelt consists of short, dense, soft underfur protected by longer, stiff, glossy guard hairs.  Air trapped within the fur acts as insulation when the otter is submerged.  Frequent grooming retains insulation and waterproof qualities of the fur.  Otter pelts range from a rich dark brown (almost black) to a pale chestnut on the back and sides and light brown mixed with varying amounts of gray on the belly.  Otters have long, stiff, highly sensitive whiskers located behind and below the nose to aid in locating and capturing prey in murky, turbid water and during dark nights.  The otter’s eyes contain a specialized lens to assist with underwater viewing.  Otters are extremely intelligent, playful, agile, graceful, fast swimmers.  If frightened or alarmed, otters can run at speeds up to 18 miles per hour.  When hunting for food in the water, otters can remain submerged for up to eight minutes.  Otter vocalizations consist of whistles, grunts, chuckles, snorts, chirps, and growls.

DISTRIBUTION:  Northern river otter populations span the North American continent from east to west, extending across 45 states from southern Florida to northern Alaska and all Canadian provinces except Prince Edward Island.  Other species of otters live on every continent except Australia and Antarctica.

HABITAT:  Northern river otters inhabit unpolluted freshwater waterways such as rivers, streams, lakes, ponds, and swamps or marshes.  An otter’s home range may be as small as five miles to as large as 40 miles.  Otters can travel several miles over land to reach another body of water to set up new territories.

FEEDING HABITS:  Northern river otters are mainly fish eaters.  They are fast, agile swimmers and able to out-maneuver their prey.  Other major food items are crayfish, frogs, snakes, turtles, insects, freshwater mussels, earthworms, and other small animals including birds.

LIFE HISTORY AND ECOLOGY:  Northern river otters are typically social animals except during spring when the female drives the male away to give birth.  Females will utilize a den in a mud bank or fallen tree trunk near the water for a nest location.  The gestation period is about two months and litter size is one to five pups, usually two.  Females allow the male to return after approximately 10 to12 weeks to assist with rearing and teaching the pups essential survival skills.  Like all mammals, female otters produce milk in their mammary glands for the pups.  Young otter pups attain sexual maturity at two years of age and at that time are driven away to establish their own territory.  Life expectancy is less than 10 years in the wild.

REFERENCES:

National Audubon Society. 1996.  Field Guide to Mammals, North America.  Chanticleer Press, Inc. 937 pp.

Novak, Mila, James A. Baker, Martyn E. Obbard and Bruce Malloch, editors.  1987.  Wild Furbearer Management and Conservation in North America.  The Ontario Trappers Association, 1150 pp.

Nora Bowers, Rick Bowen, and Kenn Kaufman. 2004. Mammals of North America.  Houghton Mifflin Co., New York, NY. 351 pp.

William H. Burt and Richard P. Grossehnheider.  1980.  Peterson Field Guide, Mammals. Houghton Mifflin Co., New York, NY. 271 pp.

Wilson, D. E. and S. Ruff. 1999. The Smithsonian Book of North American Mammals.  Smithsonian Institution Press.  Washington, D.C. 750 pp.

Author: Daniel Toole, Wildlife Biologist, Division of Wildlife and Freshwater Fisheries.

Articles: Otters in the Woods


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