Seals, sea lions, fur seals and walruses are all classed as pinnipeds. The name is derived from the Latin for flap-footed and these marine mammals are thought to have derived from bear-like ancestors which entered the sea millions of years ago.

Life span
26 years.

Statistics
Males (bulls): 2.1m, 175-275kg. Females (cows): 1.4m, 30-50kg.

Physical description
Northern fur seals have short, pointed faces with large rear flippers. Pups are black at birth but as they mature they become dark brown in coloration, with a pale patch on the neck.

Distribution
The northern fur seal is found throughout the North Pacific Ocean. The primary rookeries (breeding sites) are on the Pribilof islands and the Commander islands in the Bering Sea.

Diet
The main components of the northern fur seal's diet include fish such as herring, anchovy, pollack and capelin, as well as squid.

Behaviour
The males are territorial, and after their arrival on the rookeries from late May, will establish territories by threatening and fighting other males. These territories may contain at least 40 females.

Northern fur seals tend to live alone or in pairs, and rarely come to land, except to breed. Sharks, killer whales, and Steller sea lions will all hunt northern fur seals if they get the opportunity.

Reproduction
Males fast during the breeding season, and can lose 20 per cent of their body weight during the 1 to 2 month period. Bulls have a brief reproductive period, and few breed for more than two seasons. Nearly half the pups die before they are a year old.

Conservation status
The 2000 IUCN Red Data list considers the northern fur seal to be Vulnerable. The northern fur seal has been hunted for fur since the 18th Century, and in 1911, the North Pacific Fur Seal Convention was founded.

Commercial hunting is illegal on many of the islands, but hunting for sustainable use is still allowed. The population is estimated to be at 1,345,000-1,365,000.