Steller Sea Lion
Eumetopias
jubatus
 Physical
Appearance
When Stellers reach their adult size these animals
are the largest of all the eared seals. The average length of an
adult male is 300 cm, whereas a female is 250 cm. The big difference
between males and females are their weights. A full grown male
can weigh up to 1000 kg and a female is only 270 kg! Adult fur
is light to reddish brown in colour and adult males develop thick
neck muscles that are covered by long coarse hair, that looks like
a mane, hence the name "sea lion".
Distribution
Steller sea lions live in the Pacific northwest and can be found from San Miguel
Island in southern California, to Alaska, to the Sea of Okhotsk, near Japan.
Along the California coast north to Vancouver Island, British Columbia,
there lives a another species of sea lion, the California sea lion (Zalophus
californianus). The California sea lion is often mistaken by an untrained
eye for the Steller sea lion.
Steller
vs California Sea Lions
Here's how you can tell a Steller sea lion from a California sea lion:
Adult
Steller sea lions are lighter tan or reddish brown in colour versus the darker
brown or black coloured California sea lion
A
full grown female Steller sea lion is four times as big as a female California
sea lion
A
full grown male Steller sea lion is at least three times as a big as a male
California sea lion
Adult
male Stellers have a "mane" of thick fur around their neck, whereas
male California sea lion have a large "bump" extending from their
forehead
Steller
sea lion vocalizations sound like roars, whereas California sea lions sound
like barks
Predators
and Diet
Predators of Steller sea lions include both transient killer whales and great
white sharks. Steller sea lions are intense predators themselves, and feed
on fish, such as rockfish, sculpins, capelin, and flatfish. They also feed
on invertebrates, such as squid, octopuses, shrimps and crabs and sometimes
they will even eat northern fur seals!
Current
Status and Research
Steller sea lion populations have dropped from 300,000 to 100,000 since 1980
and are still declining. In the United States the Steller sea lion is considered
threatened and is very close to being put on the United States Endangered Species
List. However, the Steller sea lion populations appear to be relatively stable
in British Columbia, with numbers around 7,200, while the Steller populations
of Alaska are declining. Possible reasons that may
be contributing to the decline in Alaska include: an increase in parasites
and disease, predation by killer whales, nutritional stress caused by competition
with humans or other species for food and/or changes in abundance, quality
and distribution of prey, and environmental factors such as pollution.
References
Riedman, Marianne. 1990. The Pinnipeds: Seals, Sea Lions, and Walruses. University
of California Press, Los Angeles. ISBN 0-520-06497-6
Schusterman, Ronald J. 1981.
Steller Sea Lion - Eumetopias jubatus. In Handbook
of Marine Mammals. Vol. 1, The Walrus, Sea Lions, Fur
Seals and Sea Otter, ed. S. H. Ridgway and R. J. Harriso,
119-142. Academic Press, New York. ISBN 0-12-588501-6
For more information on current research
being done to answer the question "Why Steller sea lion
populations are declining?" check out these websites:
NOAA Steller Sea Lion research page
North Pacific Universities, Marine Mammal Constortium - Sea Lion research
Vancouver Aquarium: AquaFacts, Research, and
Conservation in Action
Questions
and answers about Seal Lions
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