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Endangered Species

The Sea Otter

 Enhydra lutris

The sea otter is the largest species of the weasel family and the smallest marine mammal. It resides along the west coast of North America including the Aleutian Islands. A few centuries ago, it lived along the shores from Baja California to Japan but over zealous hunting pushed them close to extinction. An estimated 150,000 to 300,000 otters may have lived along the west coast when widespread hunting began in 1741. 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 fro hunting. Otters are re-populating former haunts. Most of the area west of Prince William Sound is now recolonized. In British Columbia, populations are growing at a rate of about 18% per year and otters are now regularly seen in places on the west coast of Vancouver Island and a few places on the mainland coast. There are isolated populations in Washington and California.  Their habit of habitually swimming on their backs has made them readily identifiable and a popular attraction among the marine animals.


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. There are three recognized sub species. 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.


Sea otters live near the shore of the west coast where they eat mostly marine invertebrates. They glean the ocean bottom by making brief dives. Studies in California indicate that some individuals might specialize on a few species of prey that they appear to learn form their mothers. Food items are opened by gnawing or hammering against a rock held on its belly.   


Female otters become sexually mature at about 3 to 5 years of age. Adult males defend territories against other males. Females move freely between these territories briefly forming a bond with males for mating. Gestation requires about six months. Single pups are born annually. Males reach sexual maturity at between 5 and 7 years of age.


Young males disperse away from groups soon after weaning to establish their own territories. Females tend to stay close to where they were born. Otters will form into rafts numbering from a few individuals to several hundred otters.


The sea otter is well known for its ability to limit the distribution and abundance  invertebrate prey. They have been described as keystone species for their ability to influence the presence of other species in an ecosystem.

Sea Otter Identification

Sea Otter Distribution Maps



 Sea Otter Pictures

Sea Otter Photos by Tom Middleton

Grizzly Bear Photos by Tom Middleton

Killer Whale Photos by Tom Middleton

Blue Whale Photos by Tom Middleton



More Sea Otter Information, Sea Otter Photos and Sea Otter Video


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