Northern Fur Seal Biology - Marine Mammal Research Consortium


	common name	northern fur seal
	scientific name	Callorhinus ursinus
	Body size:	Northern fur seals are sexually dimorphic, with males considerably larger (up to 4.5 times heavier) than females Adult male northern fur seals average a nose-to-tail length of 2 m (6.6 ft) and weigh about 186 kg (410 lbs) Adult female northern fur seals average 1.3 m (4.3 ft) long and weigh about 40 kg (88 lbs) Male newborn pups weigh on average 5.7 kg (12.6 lbs) and measure about 66 cm (26 in) long Female newborn pups are smaller than male pups, and weigh on average 5.2 kg (11.5 lbs) and measure about 63 cm (25 in) long
Average life expectancy:	Females: 19 years Males: 13 years
Physical characteristics:	Fur seals have tightly rolled external ears and can rotate their hind flippers forward, allowing them to walk or run on land Distinctive characteristics of the northern fur seal are its thick, waterproof underfur and its large, bare flippers which aid in regulating their body temperature, especially on land Females: brown to gray colored coat Males: black to reddish coat developing a lighter colored mane around 6 years of age Pups: black coat Fur is a mix of a permanent dense underfur and longer guard hairs which are molted once a year in the fall (October – November) Large eyes allow them to see at night and underwater. To prevent water from entering while diving, fur seals are able to close their nostrils and their ears which have a narrow, waxy orifice
Diet:	The main components of the northern fur seal’s diet includes fish such as pollock, salmon, sandlance, northern smoothtongue, herring, anchovy and capelin, as well as squids Fur seals feed mainly at night and may dive to depths up to 200 m (656 ft) in search of small schooling fishes and squids
Habitat:	Distribution ranges from the Bering Sea to the waters off central Japan and southern California in the Pacific Ocean Most northern fur seals occur in the North Pacific Ocean during the winter and spring, and migrate to breeding islands in the Bering Sea, Sea of Okhotsk and California in the spring Breeding islands include the Pribilof Islands, Bogoslof Island, Commander Islands, Robben Island, Kuril Islands and San Miguel Island
Reproduction:	Males establish breeding territories in June in areas called rookeries Males fast during the breeding season, and can lose 20 percent of their body weight during the 3 – 4 month period Females return to the rookeries in late June to late July and give birth to a single pup, with most pups born in early July Northern fur seals mate on land usually within 11 day of giving birth Females can reproduce yearly from age 5 – 7 to age 23 years Bulls breed for an average of two seasons
Conservation status:	Commercially hunted for its luxurious fur pelts on the Pribilof Islands from 1780 – 1984 The 2000 IUCN Red Data list (World Conservation Union) considers the northern fur seal to be Vulnerable In 1988 the northern fur seal was been listed as “depleted” under the U.S. Marine Mammal Protection Act Worldwide population is approximately 1.1 million animals, with more than 70% breeding on the Pribilof Islands in the eastern Bering Sea Pribilof Island population has been declining at a rate of 6% per year since 1998