fur seal

fur seal, fin-footed marine mammal of the eared seal family (Otaridae), highly valued for its fur. Like the closely related sea lion, the nine species of fur seals are distinguished from the true seal by external ears and the ability to turn their hind flippers forward for walking on land. The northern, or Alaskan, fur seal, Callorhinus ursinus, has an outer coat of long coarse hair known as guard hair and an inner coat of thick soft fur; it is the inner coat that is valued in the fur trade. Males are dark brown and females and young are grayish. The male is about 6 ft (1.8 m) long and weighs up to 600 lb (270 kg), while the smaller female is up to 4 ft (1.2 m) long and seldom weighs more than 110 lbs (50 kg). Herds of northern fur seals, mostly females and juveniles, winter in open ocean along the Pacific coast of North America, migrating in spring to breeding beaches that range from the Pribilof Islands in the Bering Sea to San Miguel Island off California. Adult males, who usually winter separately, arrive at the islands weeks ahead of the females. During the breeding season the most aggressive males establish individual territories and have harems averaging 40 to 50 females, which they defend against other males. Mating occurs after the birth of the young conceived the previous summer; each female bears a single pup after a gestation period of almost a year. The pups nurse for about a month but remain with the mother for another 2 or 3 months. Mothers often leave pups for days to feed on squid and fish. By the early 20th cent. the northern fur seal population was reduced to about 200,000 as the result of wanton slaughter. An international treaty signed in 1911 limited hunting to a fixed number of nonbreeding males per year. By 1976 the world population had increased to almost 2 million; since then it has declined, for reasons still unclear. The United States prohibited the hunting of fur seals in 1985. Southern fur seals, such as Arctocephalus gazella and other species, are similar in size and appearance to the northern fur seal. Although their fur is not considered desirable, they have been hunted almost to extinction. Both southern and northern fur seals migrate, while tropical species remain near their breeding grounds. Fur seals are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Carnivora, suborder Pinnipedia, family Otariidae. See also Bering Sea Fur-Seal Controversy, under Bering Sea.

See W. N. Bonner, Seals and Man (1982); J. E. King, Seals of the World (1983).

The Columbia Electronic Encyclopedia Copyright © 2004.
Licensed from Columbia University Press

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fur seal

Any of nine species of eared seals valued for their fur, especially the chestnut-coloured underfur. Fur seals live in groups and feed on fish and other animals. They were driven nearly to extinction by fur hunters, and most species are now protected by law. The northern fur seal (Callorhinus ursinus) is a migratory inhabitant of northern seas. The male is deep brown, has a grayish mane, grows to about 10 ft (3 m) long, and weighs about 650 lb (300 kg). The dark gray female is much smaller. The eight species of southern fur seals (genus Arctocephalus) occur in the Southern Hemisphere and on Guadalupe Island, Mex. They are brown or black and average 4–6 ft (1.2–1.8 m) long.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.

Fur seal

Fur seals are any of nine species of pinnipeds in the Otariidae family. One species, the northern fur seal (Callorhinus ursinus) inhabits the North Pacific, while seven species in the Arctocephalus genus are found primarily in the Southern hemisphere. They are much more closely related to sea lions than true seals, and share with them external ears (pinnae), relatively long and muscular foreflippers, and the ability to walk on all fours. They are marked by their dense underfur, which made them a long-time object of commercial hunting.

Taxonomy

Until recently, fur seals were all grouped under a single subfamily of Pinnipedia called Arctocephalinae to contrast them with Otariinae - the sea lions - based on the most prominent common feature, namely the coat of dense underfur intermixed with guard hairs. Recent genetic evidence, however, suggests that Callorhinus is more closely related to some sea lion species, and the fur seal/sealion subfamily distinction has been eliminated from most taxonomies. Nonetheless, all fur seals have certain features in common: the fur, generally smaller sizes, farther and longer foraging trips, smaller and more abundant prey items and greater sexual dimorphism. For these reasons, the distinction remains useful.

Physical appearance

Fur seals share with other otariids the ability to turn their rear limbs forward and move on all fours. Fur seals are generally smaller than sea lions. At under 1 m, the Galapagos fur seal is the smallest of all pinnipeds. However, their flippers tend to be proportionately longer, their pelage tends to be darker and the vibrissae more prominent. Males are often more than five times heavier than the females, making them among the most sexually dimorphic of all mammal groups.

Behavior and ecology

Typically, fur seals gather during the summer months annually in large assemblages at specific beaches or rocky outcrops to give birth and breed. All species are polygynous, meaning dominant males reproduce with more than one female. For most species, total gestation lasts about 11.5 months, including a several month period of delayed implantation of the embryo. While northern fur seal males aggressively select and defend the specific females in their harems, males of southern species of fur seal tend to protect spatial territories and females are free to choose or switch their mates according to their own preference or social hierarchy. After several continuous days of nursing the newborn pups, females go on extended foraging trips that can last as long as a week, returning to the rookery to feed their pups until they are weaned. Males fast during the reproductive season, unwilling to leave their females or territories.

The remainder of the year, fur seals lead a largely pelagic existence in the open sea pursuing their prey wherever it is abundant and plentiful. Fur seals feed on moderately sized fish, squid and krill. They are preyed upon by sharks, orcas, and occasionally by larger sea lions.

When fur seals were hunted in the late eighteenth and early nineteenth centuries, they hauled out on remote islands where there were no predators. The hunters reported being able to club they unwary animals to death one after another, making the hunt profitable even though the price per seal skin was low.

Exploitation

Many fur seal species were heavily exploited by commercial sealers, especially during the 19th century when their fur was highly valued. Beginning in the 1790s, the ports of Stonington and New Haven, Connecticut were leaders of the American fur seal trade, which primarily entailed clubbing fur seals to death on uninhabited South Pacific islands, skinning them, and selling the hides in China. Many populations, notably the Guadalupe fur seal, northern fur seal and Cape fur seal, suffered dramatic declines and are still recovering. Currently, most species are protected and hunting is mostly limited to subsistence harvest. Globally, most populations can be considered healthy, mostly due to the fact that they often prefer remote habitats that are relatively inaccessible to humans. Nonetheless, environmental degradation, competition with fisheries and climate change potentially pose threats to some populations.