The Steller (or northern) sea lion (Eumetopias jubatus) inhabits the north Pacific Ocean and is the largest member of the family of Otariidae, or "eared seals." Sea lions differ from hair seals (harbor seals, ringed seals, ribbon seals, bearded seals, and spotted seals) in that sea lions have external ears and rear flippers which turn forward allowing them to "walk" with a gait similar to land mammals.

They are called sea lions because they resemble the terrestrial lion of Africa and Asia. Large adult male Steller sea lions have disproportionately large necks and shoulders. This, coupled with longer, coarser hair on the neck and shoulders, gives them the appearance of having manes, as do lions.

General description: At birth, the sea lion pup's coat is chocolate brown with a frosty appearance because the tips of the hair are colorless. Color gradually lightens as the animal ages and periodically molts. Most adult females are a yellowish, cream color on the back, although some remain darker. Nearly all males stay darker on the front of the neck and chest; some are even a reddish color.

Males and females have a marked size difference. Weight at birth is 51 pounds (23 kg), and body length is 45 inches (112 cm). Females grow rapidly during the first four years but slow by the fifth year, with little growth after age 6. Males continue to grow until the eleventh year. Although there are variations, most females reach maximum size by the seventh year, and males reach adult size by the twelfth year. The average weight of an adult male is 1,245 pounds (566 kg), and the body length averages 10 2/3 feet (282 cm). Adult females average 579 pounds (263 kg) in weight and 8 2/3 feet (228 cm) in length. Although only 20 percent longer, the average adult male weighs over twice as much as the average adult female.

Life history: Steller sea lions gather on well-defined, traditionally-used rookeries to pup and breed. Males defend individual territories from approximately mid-May through mid-July. They mate with females which give birth, then come into estrus in their territory. Females give birth to a single pup anytime from mid-May through July. They breed shortly after giving birth, but the fertilized egg does not implant in the uterus and begin growing until October. Some females first breed in their third year, producing young in their fourth year. By their sixth year, nearly all females are breeding and producing pups. Males are physiologically able to breed at 3 to 6 years, but they probably do not participate until after 8 to 10 years because of strong territorial competition among the largest males.

Age at weaning varies among Steller sea lions; some pups are weaned in the first year, while others may suckle until 3 years of age. At birth the sex ratio seems to favor males slightly. Twins occur rarely.

Distribution and migration: Steller sea lions are found from the northwestern California coast northward into the Bering Sea to Bering Straits, in the Okhotsk Sea and along the Kamchatka Peninsula in Russia, in the Kurile and Commander islands, and south as far as Hokkaido and northern Honshu in Japan. In the 1970s, the worldwide population of Steller sea lions was about 281,800, with the Alaska population estimated at 242,000, including pups. The number of sea lions in Alaska declined by 50 percent from the mid-1970s to the mid-1980s.

Seasonal movements occur generally from exposed areas in summer to protected areas in winter. Steller sea lions can move over long distances. The longest recorded movement was by an animal marked at Marmot Island near Kodiak and taken near Ketchikan, a distance of approximately 900 miles (1,645 km).

Food habits: As marine carnivores, Steller sea lions eat a wide variety of fish such as pollock, flounder, herring, capelin, Pacific cod, salmon, rockfish, sculpins, and invertebrates such as squid and octopus. Most of the top-ranked prey of sea lions are off-bottom, schooling species. Feeding occurs from the intertidal zone to the continental shelf, and Steller sea lions are considered top level consumers.

Human uses: Steller sea lions were historically a primary source of food for inhabitants of the Aleutian Islands. Clothing, boots, and boat coverings were made from skins. The Chinese once used Steller sea lion whiskers for cleaning opium pipes. Fur farmers used Steller sea lion meat for fox food along the Alaska coast. Between 1964 and 1972, Steller sea lion pups were commercially harvested. The hides were used in manufacture of coats, boots, gloves, and other garments. Since 1972 (after passage of the Marine Mammal Protection Act) and into the 1980s, there has been little use of Steller sea lions, although some are still taken by Alaskan Natives for food around Kodiak Island, the Aleutians, and the Pribilof Islands.

Text: Don Calkins
Illustration: Riedner
Revised and Reprinted 1994