River Otter, North American

ORDER: Carnivora

FAMILY: Mustelidae

GENUS: Lutra

SPECIES: canadensis

Long, slender, sleek body, weighing approximately 20 pounds (9 kg) and about two and a half feet (76 cm) long. 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 a third smaller than males.

All of the United States and Canada except the tundra and parts of the arid southwestern United States. Allied species occur in Mexico, Central and South America, as well as Eurasia. Found in streams, rivers, lakes, estuaries, and salt- and freshwater marshes.

Fish, crayfish, 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. Zoo diet: fish or horse meat with vegetables. Feline diet with fish three times a week and vitamin E twice a week.

Spends two-thirds of the time on land. 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 youngsters 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 an obscure 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.

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. They seem to enjoy frolicking in ice and snow. 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, pulse slows to a tenth of the normal rate of 170 beats a minute, thereby conserving oxygen. Both diurnal and nocturnal.

Otter droppings are called spraints. King James I of England kept a pack of tame otters to catch fish for his table, even appointing a "Keeper of the King's Otters" to tend them.

3 Males. 2 Females. Our female gave birth to two pups (a male and female) in February 2011.

The river otter is native to northern and central California, being found in the delta region of the Sacramento and San Joaquin Rivers, where it sometimes dens in thick tules. In California the river otter is fully protected under law and may not be taken at any time. Listed on the IUCN Red List as Low Risk.


  1. Grzimek, Bernhard. 1972. Animal Life Encyclopedia, Vol. 12, Van Nostrand Reinhold Co, New York.
  2. Internet: IUCN Red List.
  3. Leopold, A. Starker, Ralph Gutierrez and Michael Bronson. 1981. North American Game Birds and Mammals. Charles Scribner's Sons, New York.
  4. MacDonald, David. 1987. Encyclopedia of Mammals, Facts on File, New York.
  5. Nowak, Ronald. 1991. Walker's Mammals of the World, 5th Ed., Vol. II, Johns Hopkins University Press, Baltimore, MD.