Common Harbor Seal

Common or harbor seals (Phoca vitulina) are small, stocky seals found throughout the temperate and Arctic waters of the Northern Hemisphere. They have the widest distribution of any pinniped. In the eastern Atlantic, they are found throughout the British Isles, the North Sea, Iceland, and all along the coast of Norway, as far north as Finnmark. Their range extends across the Atlantic to Greenland, and in North America from Baffin and Hudson bays as far south as Long Island, New York City, and New Jersey. They can be found on both sides of the Pacific, from Herschel Island around Alaska and along the west coast of North America as far south as Baja California.

Harbor seals occur throughout the Aleutians, the Commander Islands, the Kurils and the Pribilofs, as well as Kamchatka and Hokkaido. A rough estimate of the world population of harbor seals is around 500,000.

Throughout their vast range, there is much variation in size, morphology and behavior, and some workers recognize subspecies such as P. vitulina richardsi of the coastal eastern Pacific, P. vitulina stejnegeri of the western Pacific and the Sea of Japan, and P. vitulina kurilensis of the Kuril Islands, but others lump them all together. Most current studies recognize Phoca largha, the spotted seal, as a distinct species, although it used to be considered conspecific with P. vitulina. (Harbor seals breed on land, while spotted seals breed on ice.) There is great variety in the coloration of these seals, ranging from silvery gray with dark spots to dark brown and almost black with silvery or whitish rings. Pups are born with short coats like those of adults. Some populations are nonmigratory, breeding and feeding in the same area throughout the year, but others may migrate for hundreds of miles. Males and females mature at about 5-7 years of age, and females produce a calf every year. The life expectancy for both sexes is 25-30 years. In Alaska and the western Pacific, where harbor seals are larger than those of the Atlantic, adult males which are consistently larger than females can be over 6 ft (1.9 m) in length, and weigh up to 330 lb (150 kg). Compared to other similarly sized phocids, for example, the harp or ringed seals, the skull of P. vit-ulina is more thickly boned, and the teeth, especially the postcanines, are broad and heavy. In order to eat bivalves, they crush them with their teeth. Harbor seals are considered the least vocal of all pinnipeds; after weaning, their vocalizations are restricted to snorts, grunts, or growls, and they probably do not emit echolocation clicks. They can be confused with young gray seals because their ranges overlap in many parts of the Atlantic, but harbor seals are usually smaller, and they can be further differentiated by the nostrils: those of the harbor seal are arranged in a wide "V," while those of the gray seal are nearly parallel.

Like all the other phocids, the harbor seal uses its hind flippers for propulsion in the water, but on land it hitches along, using only its fore flippers, which are equipped with sturdy claws. When resting on land or rocks, harbor seals often assume a bananalike pose with the head and hind flippers elevated. Harbor seals occasionally haul out on rocks long before low tide, and remain on seemingly inaccessible positions until the tide comes in and they are able to swim off. Newly weaned pups feed on bottom-dwelling crustaceans and amphipods; adults eat almost anything they can catch, including various cephalopods and crustaceans, but the staple of their diet is fish, such as herring, anchovies,

Common harbor seal (Phoca vitulina).

Photo by Sue Matthews, courtesy US Fish and Wildlife Service

Common harbor seal (Phoca vitulina).

Photo by Sue Matthews, courtesy US Fish and Wildlife Service

trout, smelt, codfish, rockfish, greenling, sculpin, sandlance, and various flatfish. They are accomplished divers, and have been recorded as making feeding dives up to 1500 ft (446 m) In the water, they are preyed upon by sharks and killer whales; and northern sea lions and eagles take an occasional pup on land.

In earlier days, Inuit hunters harpooned various species of phocids on the ice and in the water, but with the introduction of firearms they resorted to the more efficient method of shooting them. Unlike the ringed or bearded seals, harbor seals do not use breathing holes, but climb out of the water on sandbars or icefloes. They must be approached carefully because the first shot often drives the whole group into the water. Unlike other seals, which attempt to escape when wounded, harbor seals sometimes turn on the hunters or dive deeply, and are considered dangerous to hunt. Where the ocean surface does not freeze solid, seals come to open spaces between ice-floes for air; in these areas, Inuit hunters pursue the seals in kayaks or stand by the floes, hoping for a chance to throw their harpoons. After the Inuit hunter locates such a space, he stand with a poised harpoon, awaiting the quivering of a small, slender piece of baleen, or whalebone, stuck through the thin ice surface, which signals the seal's surfacing. Often the hunter has to stand this way for hours in the bitter cold. When the baleen marker began to jiggle, he threw the harpoon, which was constructed so as to embed itself and remain fixed in the fat layer of the stricken animal. The harpoon head, connected to a float of inflated sealskin by a line about 33 ft (10 m) long, would not only mark the location of the wounded animal but would also hamper its escape.

Traditionally, Inuit used nearly all the parts of killed seals; the blubber fuelled the soapstone lamps that provided light and warmth, and the skin was fashioned into hooded parkas, mittens, pants, and waterproof boots, which were particularly well adapted to cold and wet climatic conditions. The skin of the harbor seal is thicker and heavier than that of the ringed seal, and was also used to make whips, boots, and dog harnesses. The skins were also processed into tents and boats, and the bones were made into weapons, but seal meat and oil were the staples of the Inuit diet. Some Inuit still wear sealskin clothing, but it has largely been replaced by commercially available waterproof fabrics and down-filled garments.

Europeans hunted harbor seals in Alaska, Greenland, northern Canada, and Russia with nets and guns. Their short, silky fur was made into sports clothing in Europe, particularly ski parkas. The seals' raids on fish stocks and fishermen's nets have made them unwelcome in various countries, and hundreds of thousands have been killed by bounty hunters in Alaska, British Columbia, Washington, Oregon, Massachusetts, Norway, and the British Isles. Many are also drowned in gill nets.

In recent years, various populations of harbor seals have been decimated by phocine distemper virus (PDV), a pathogen that closely resembles and, indeed, seems to have been derived from canine distemper virus (CDV). In 1979-1980, some 400 harbor seals died in New England, and in 1988, nearly 18,000 died in the North Sea, along the shores of Denmark, Sweden, and Great Britain.

Richard Ellis

See also Spotted Seal Further Reading

Bigg, M.A., "Harbour Seal—Phoca vitulina Linnaeus, 1758 and Phoca largha Pallas, 1811." In Handbook of Marine Mammals, Volume I1: Seals, edited by S.H. Ridgway & R.J. Harrison, San Deigo: Academic Press, 1981, pp. 1-27 Burns, J.J., "Harbor Seal and Spotted Seal."In Encyclopedia of Marine Mammals, edited by W.F. Perrin, B. Wursig & J.G.M. Thewissen, London and San Diego: Academic Press, 2002 Bruemmer, F., Encounters with Arctic Animals, New York:

American Heritage, 1972 Clark, A.H., "The North Atlantic Seal Fishery." In The Fisheries and Fishery Industries of the United States. Section 5, Volume 2, edited by G.B. Goode, Washington: General Printing Office, 1887, pp. 474-483 Kennedy, S., "Morbillivirus infections in marine mammals."

Journal of Comparative Pathology, 119 (1998): 201-225 King, J.E., Seals of the World, Ithaca: Cornell University Press, 1983

Nelson, R.K., Hunters of the Northern Ice, Chicago: University of Chicago Press, 1969

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