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Sea Otter Enhydra lutris


The sea otter is the largest species of the weasel family and the smallest marine mammal. It is sociable and endemic to northern Pacific Ocean. Three subspecies are recognized; Enhydra lutris kenyoni occurs in Washington north through the Aleutian Islands, Enhydra lutris lutris occurs in the Commander Islands to northern Japan, and Enhydra lutris nereis is found in California.

A few centuries ago, as many as 300,000 otters lived along the shores from Baja California to Japan. Widespread hunting beginning in 1741 extirpated the otter from most of the coast. The numbers slowly began to recover following a treaty in 1911 between the United States, Japan, Russia and Great Britain provided the otter with protection from hunting. Otters are re-populating former haunts. Most of the area west of Prince William Sound is now recolonized. In British Columbia, Alaska and Washington, populations are growing at a rate of about 20% per year and otters are now regularly seen in places on the west coast of Vancouver Island and a few places on the British Columbia mainland coast. They are also present along much of the Washington, Oregon and California coast. The California population growth is about 5% per year.  

The sea otters distinguishable features include large flipper like hind limbs, flattened molars and flattened tail. Males measure about 1.2 to 1.4 meters in length and females are about 1.0 to 1.4 meters long. Males weigh up to 45 kilograms and females reach 33 kilograms. Otters that reach adulthood can live for about 15 to 20 years in the wild.




Cronin, M.A., Bodkin, J., Ballachey, B., Estes, J., and Patton, J.C. 1996. Mitochondrial-DNA variation among subspecies and populations of sea otters (Enhydra lutris). Journal of Mammalogy 77(2):546-557.

Ebert, E. 1968. A food habits study of the southern sea otter Enhydra lutris. California Fish and Game 54: 33042.


Estes, J.A. and Palmisano. 1974. Sea otters: their role in structuring nearshore communities. Science 185: 1058-1060.


Estes, J. A., N. S. Smith and J. F. Palmisano. 1978. Sea otters predation and community organization in the western Aleutian islands, Alaska. Ecology 59: 822-833.


Foott, J. O. 1970. Nose scars in female sea otters. Journal of Mammalogy 51: 621-622.


Garshells, D. L. and J. A. Garshells. 1984. Movements and management of sea otters in Alaska. Journal of Wildlife Management 48: 665-678.


Hall, E. R. and G. B. Schaller. 1964. Tool-using behaviour of the California sea otter. Journal of Mammalogy 45: 287-298.


Houk, J. L. and J. J. Geibel. 1974. Observations of underwater tool use by the sea otter Enhydra lutris. California Fish and Game 60: 207-208.

Kenyon, K. W. 1975. The sea otter in the eastern Pacific Ocean. Dover, New York.


Love, J. A. Sea otters. 1992. Fulcrum Press, Colorado.


Loughlin, T. R. 1980. Home range and territoriality of sea otters near Monterey, California. Journal of Wildlife Management 44: 576-582.

McShane, L.J., Estes, J.A., Reidman, M.L., and Staedler, M.M. 1995. Repertoire, structure, and individual variation of vocalizations in the sea otter. Journal of Mammalogy 76(2):414-427.

Payne, S. F. and R. J. Jameson. 1984. Early behavioural development of the sea otter Enhydra lutris. Journal of Wildlife management 65: 527-531.


Shimek, S. J. 1977. The underwater foraging habits of the sea otter Enhyrda lutris. California Fish and Game 63: 120-122.


Simenstad, C. A., J. A. Estes and K. W. Kenyon. 1978. Aleuts. Sea otters and alternate stable-state communities. Science 200: 403-411.


Wilson, D. E. and S. Ruff. 1999. The Smithsonian book of North American mammals. Smithsonian

Institution, Washington, D.C.













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