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Eumetopias jubatus (Schreber, 1776)Northern Sea-Lion; Steller sea lion; Phoca; Northern sea lion |
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Eumetopias jubatus
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By Michelle Gonder
Steller's Sea Lion is found on the North Pacific coasts. The countries included are Russia, Japan, Canada, and part of the United States. More specifically it is found from the sea of Japan at 43 degrees N, north to the Pacific rim at 66 degrees N, and then south down to the North American Pacific coast to San Miguel Island at 34 degrees N.
Biogeographic Regions:
nearctic
(
native
);
palearctic
(
native
).
This species is the largest of five species of seals belonging to the family Otariidae (eared seals). It is characterized by a yellowish buff color, and a coat of short coarse hair that lacks a distinct undercoat. Sea lions have longer flippers than the true or earless seals. They are capable of rotating their hind flippers forward in order to have full use of all four limbs on land.
Steller's Sea Lions show remarkable sexual dimorphism. Males are much larger than females. The length of the average male is 282 centimeters, while the length of the average female is only 228 centimeters. The weight of the average male is 566 kilograms, while the weight of the average female is only 263 kilograms. Males also have extremely thick muscular necks and a mane of coarse long hair.
Newborn pups are about 100 centimeters long, weigh 16-23 kilograms, and have a thick, dark brown pelage that molts to lighter after six months. After 2-3 years their color changes again, this time to the adult color.
Some key physical features:
endothermic
;
bilateral symmetry
.
Mating generally occurs in May. Males establish a harem of 3-20 females and a territory surrounding them. The pups from the preceding season are born from late May to early June. Shortly after giving birth, the female is impregnated again. Sixty to sixty seven percent of all females are impregnated every year. Implantation of the fertilized egg is delayed for three months giving Steller's Sea Lion a twelve month gestation period. The new pups are fed by their mother for a minimum of three months and sometimes up until the next pup is born. The pups are able to swim after one month, and can catch food after approximately three months. The age of maturity is 3-6 years for females, and 3-7 years for males. On average, females live 30 years. Males, subject to injury in violent encounters with other males, typically live only 18 years.
Key reproductive features:
gonochoric/gonochoristic/dioecious (sexes separate);
sexual
.
Male Steller Sea Lions (bulls) are extremely aggressive and territorial. They are large animals and often fight for mates. They do this by throwing their huge bodies up against one another and biting. They come to the breeding ground in May, and this is when the fighting begins. The strongest bull is the male with the largest harem.
Steller's Sea Lions are not often found in captivity. This is due to their belligerent nature. They are thought to be dangerous to have in zoos, and untrainable for circuses.
They acquire their food by diving into the ocean. The deepest recorded dive by one of these huge beasts was 120-160 yards. This particular animal was found caught in a net, so this number could be slightly inaccurate.
Sea Lions are also known for their "sun bathing". They are most often viewed by boaters and tourists as they lay in the sunshine on the rocks.
Studies are now being done on the communication of Steller Sea Lions. They are believed to make certain clicking noises when hunting and swimming and can produce a low roaring sound similar to that of a lion.
Key behaviors:
motile
.
Steller's Sea Lions are known to be true carnivores. They feed on both commercial and non-commercial fish, and also on cephalopods (octopus and squid). Commercially exploited walleye pollack is an important part of their diet. This selective diet is a major cause of the Sea Lions' diminishing population, due to competition with humans for this favorite.
Eats many commercial fish that humans exploit.
Profit from meat, hides, and blubber. Ecotourism benefits greatly from sea lions because humans think that they are "cute".
They are a primary source of food for inhabitants of the Aleutian Islands. Their skins can be used for boat coverings, clothing, and their whiskers for cleaning of Chinese opium pipes. Since the passage of the Marine Mammal Protection Act (1972), the use of these sea lions has declined.
These animals are a threatened species. The Steller sea lion was placed on the Endangered Species list in 1990. The Western Alaskan population was reclassified as Endangered in April 1997. This is due to a number of causes. Thousands were once killed each year in the nets of fishermen in Alaska. Changes in fishing techniques and gear in 1984 reduced the number killed. An unknown number are shot each year during commercial fishing because this species is seen as a pest to the industry. The Steller Sea Lion eats a variety of commercial fish. The intense commercial fishing of pollock, a major food source, has decreased the Alaskan population from 175,000 animals in 1962 to 40,000 in 1992. They are also caught in plastic trash, which usually leads to death. This species is also hunted on a small scale for subsistence and for trade.
The Steller Sea Lion is protected in the United States and the Commonwealth of Independent States (CIS) is proposing to add the species to the "red" species list.
Find Eumetopias jubatus information at
Michelle Gonder (author), University of Michigan.
To cite this page: Gonder, M. 2000. "Eumetopias jubatus" (On-line), Animal Diversity Web. Accessed February 09, 2010 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Eumetopias_jubatus.html.
Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students . ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.
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