Northern fur seal

Callorhinus ursinus

SUBFAMILY

Arctocephalinae

TAXONOMY

Callorhinus ursinus (Linnaeus, 1758), "Bering Island." OTHER COMMON NAMES

English: Sea bear; French: Otarie des Pribilofs; German: Nördliche Pelzrobbe; Spanish: Lobo fino del norte.

PHYSICAL CHARACTERISTICS

Males to 606 lb (275 kg), gray to black or reddish. Females to 110 lb (50 kg), gray. Rear flippers long and slender; hair on front flippers stops abruptly at the wrist joint. In all other otariids hair extends beyond the wrist joint.

DISTRIBUTION

The species breeds from southern California to the Kuril Islands with the main populations at the Pribilof and Commander Island groups. Females and juveniles forage south to 35°N latitude, then migrate back to breeding sites in spring.

HABITAT

This species now breeds exclusively on islands (formerly on the mainland). One of the breeding sites is known to have been used for over 250 years. It is one of the most pelagic otariids, spending all but 35-45 days per year at sea.

BEHAVIOR

It follows the basic otariid behavior, described above. It forms only a few large breeding colonies where males fast while defending terrestrial territories. Females arrive on predictable dates, form amorphous social groups, give birth, mate, then alternate foraging with nursing until weaning at four months. Females and males are highly site specific.

FEEDING ECOLOGY AND DIET

The species takes over 75 species of fish and cephalopods, many of them associated with the deep scattering layer. The diet was determined by extensive collections at sea.

REPRODUCTIVE BIOLOGY

Polygymous. The notion of seal harems may have developed with this species. The species does not deviate from the basic otariid pattern, except that females wean young at four months of age. More is known of its reproductive biology than other species because an international treaty (1911 to 1985) mandated certain kinds of research.

CONSERVATION STATUS

The species is listed as Vulnerable, and numbered only a few hundred thousand in 1911, increased to 2.5 million in the mid 1950s, then declined to approximately 1 million in 2002. The

I Callorhinus ursinus I Arctocephalus gazella I Eumetopias jubatus reasons for the decline are unknown, but it is proceeding in parallel with decreases in the Steller sea lion, harbor seal, and sea otter in Alaska.

SIGNIFICANCE TO HUMANS

The species was of great significance to society from the 1860s to 1985 because of pelts. It was the first marine mammal to which a management regime was applied, and it was the subject of an international treaty in 1911. Presently Alaska natives use the species for subsistence. ♦

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