Sea otter – biology fast facts

Common Name:

Northern Sea Otter, Southern Sea Otter, Russian Sea Otter

Scientific Name:

Enhydra lutris kenyoni (Northern), Enhydra lutris nereis (Southern), Enhydra lutris lutris (Russian)


Sea otters typically inhabit nearshore coastal waters of less than 54 m in depth. Northern sea otters are found in Russia, British Columbia, Alaska, and Washington. Southern sea otters are found along the coasts of California and Russian sea otters are found in Russia and Japan typically.

Body size:

Sea otters typically have a maximum weight of 45 kg and are 1 to 1.5 meters when fully grown.

Physical Characteristics:

Sea otters have a dark colored coat, typically darker shades of brown, with sparse guard hair and dense, insulating fur that traps air and prevents water from making contact with the skin. They have retractile claws on the front feet and a loose flap or pouch of skin under each foreleg which is used to hold food items gathered from the sea bottom. Their molar teeth are flattened and rounded with no cutting cusps. Their hind feet and tail are flattened and both aid in propulsion. Sea otters swim underwater by means of vertical undulations of the hind flippers and tail. They also external ear that resembles the ear of an otariid more than that of its closest relative, the river otter.

Life expectancy:

Males: 10 to 15 years; Females: 15 to 20 years

Behaviour (e.g. sounds, foraging):

Otters are often observed using rocks to pound small, hard bodied prey items to gain access to the edible fleshy interior.They dive to the When resting, sea otters often lie on their backs among kelp or in quiet water. The most common position is with the head up, and with folded paws and chin resting on the chest. The otter’s ‘whine’ and ‘squeal’ that is commonly heard during courtship has been found to consist of graded signals that vary over a continuum. There is a degree of complexity and richness of communication patterns believed to have evolved as a result of complex social relationships.


Fish and marine invertebrates, including various species of mussels, tunicates, sea stars, bivalves, crabs, abalone and octopus.

E. lutris  demonstrates significant selectivity and intelligence when foraging and consuming its prey. Otters can detect and avoid toxic shellfish if suitable low toxicity prey are available.


Predators of sea otters include sharks and killer whales. For young otters, larger males are considered predators.


Mating is aquatic and often involves violent and prolonged copulations during which the male approaches the female from behind and grasps her face and nose with his teeth, sometimes pulling her head underwater while attempting to subdue her. Some females may form pair bonds with a single male while others may mate with up to three different males during a single estrous period. Most females reach sexual maturity between 2-5 years of age, with 88% maturing by age 4. Most females have been observed to have the first pup by 3-4 years of age. Reproductive rate is maximal at 5 years of age and remains stable through to age 15. Female otters typically mate numerous times during their estrous period, which lasts several days and occurs about once each year. If a female loses her pup before weaning age, she may enter estrus and mate repeatedly two or more times in a single year. Mean gestation period is approximately 218 days; mean pup dependency period is about 153 days. The majority of pups are born in spring (February) and early summer. Groups of females periodically bring their young pups ashore to rest in a process known as hauling.  Female reproductive rates and pup survivorship are generally higher in undisturbed areas with abundant food sources.


There are an estimated 13,000 sea otters in Russia, 60,000-90,000 in Alaska, 800 in Washington, and 2,000 otters in California. In British Columbia there is an estimated 2,500-3,000 sea otters. The increasing population trend in B.C. has slowed in recent years because some populations appear to be at equilibrium.


Conservation status:

Sea otters were designated as “Threatened” in 1996 by the Committee of the Status of Endangered Wildlife in Canada (COSEWIC) and through the B.C. Wildlife Act protected by the federal government’s Canada Fisheries Act and the B.C. Wildlife Act. California populations are protected by the Marine Mammal Act and the U.S. Endangered Species Act.

See: Species At Risk Public Registry