Sea Otter

Illustration by Uko Gorter

Sea otters are the largest member of the weasel family, and the smallest marine mammal. They have paw-like front limbs with “pockets” that help them hold food while foraging, and they sometimes use rock “tools” to crush shelled prey.

Sea otter were heavily hunted for their thick, luxurious fur, and were nearly extinct in the Pacific Northwest by the early 1900s. A small population was transplanted from Alaska to Washington and B.C. coastal locations in the 1970s. The population rebounded, and today there is a growing number of sea otters in Washington state waters.

The best places to see them are sites along the Olympic Coast such as La Push, Rialto and Kalaloch; and in the Strait of Juan de Fuca at Shipwreck Point and Snow Creek.

Range

There are three subspecies of sea otters, two of which are found in the United States.

  • The Southern, or California sea otter (Enhydra lutris nereis) is rare and declining at a disturbing rate.  T
  • he Northern sea otter (Enhydra lutris kenyoni) is found in Washington, Alaska and Canada, and populations are growing on the Pacific Northwest coast.  They prefer to live in rocky coastal areas and can be viewed in sites along The Whale Trail such as La Push and Neah Bay.  
  • The third subspecies, the Russian sea otter (Enhydra lutris lutris), is found in Russia and Japan.

Biology

All sea otters lack insulating blubber, and rely on their thick fur and high metabolism to maintain body heat.  Sea otter fur is the thickest in the world and can have up to one million hairs per square inch. This fur insulates the body by keeping a layer of warm air between the outer surface and skin. 

Sea otters spend much of their day foraging for more than fifty kinds of marine invertebrate prey including mussels, clams, abalone, octopuses, crabs and sea urchins. They burn calories at three times the rate of humans and must consume 20-30% of their body weight daily. 

Sea otters are monagamous and become sexually mature at 3-5 years old.  Mating occurs year round.  A female otter is pregnant for about eight months and usually gives birth to a single pup weighing 3-5 pounds. Female sea otters are generally excellent mothers while males don’t participate in rearing the pubs.  The mother nurses the pup for 6-8 months and averages one new pup every 2 years.

Social Structure and Behavior

Sea otters are normally seen swimming or resting on their backs, but when moving rapidly, will swim on their bellies. 

  • Sea otters rarely go onto shore in contrast to their smaller cousins, the river otters, who spend about half their time on land and can live in either fresh or salt water ecosystems. 
  • Surface eaters, sea otters use their powerful forepaws and jaw muscles to crush prey.
  • They can dive up to 300 ft and remain underwater for up to five minutes to hunt for food. Mothers may leave their pups tucked between kelp fronds while they dive for food.

Sea otters are social animals, and gather in rafts (groups) ranging from a few dozen to over one hundred animals.  Rafts are sexually segregated as females avoid male feeding areas.

Current and Historical Threats

Hundreds of thousands of sea otters once lived along most of the Northern Pacific coast before traders hunted them nearly to extinction for their thick, luxurious pelts.  By 1911 fewer than 2,000 otters remained worldwide. 

In the 1960s and 70s sea otters from Alaska were relocated to sites along the coasts of Washington and British Columbia.  Today there are currently over 1,000 sea otters living on Washington’s outer coast and the western Strait of Juan de Fuca. 

The otters are still facing conservation threats, however, and California sea otters are listed as threatened under the Endangered Species Act (ESA). 

Oil spills are the most serious modern concern.  When sea otters are exposed to oil it destroys the insulating properties of their fur and contaminates their food. 

Commercial fishing gear including gill nets can ensnare otters and commercial over harvesting of invertebrates (e.g., abalone and sea urchins) may threaten their habitats. 

Sea otters are also at increased risk of diseases and parasites contracted from animals on land.  One way to help is to bag and dispose of cat litter instead of flushing.

Learn More!

Books:

A Raft of Sea Otters by Vicki Leon, 2005

A Lot of Otters (Picture Puffins) by Barbara Berger, 2000

Sea Otters by G. R. VanBlaricom, 2001

Links:

http://oceanlink.island.net/seaotterstewardship/index.html

http://www.defenders.org/wildlife_and_habitat/wildlife/sea_otter.php

http://animals.nationalgeographic.com/animals/mammals/sea-otter.html

Sources

Seattle Aquarium volunteer training materials
http://oceanlink.island.net/seaotterstewardship/index.html

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Facts

Length

Adult ♂ : 5 ft (1.5 m)

Adult ♀ : 4 ft (1.2 m)

Birth Length :10 in (0.3 m)

Weight

Adult ♂ : 70 lbs (32 kg)

Adult ♀ : 60 lbs (27 kg)

Birth Weight : 5 lbs. (2.3 kg)

Life Expectancy

10 – 15 years

Photos

The Whale Trail is a nonprofit organization in partnership with
Partners NOAA Seattle Aquarium People for Puget Sound Washington Department of Fish and Wildlife The Whale Museum National Marine Sanctuaries