Definitions

seal

seal

[seel]
seal, carnivorous aquatic mammal with front and hind feet modified as flippers, or fin-feet. The name seal is sometimes applied broadly to any of the fin-footed mammals, or pinnipeds, including the walrus, the eared seals (sea lion and fur seal), and the true seals, also called earless seals, hair seals, or phocid seals. More narrowly the term is applied only to true seals. The so-called performing seal of circuses is actually a sea lion.

Characteristic Features of All Seals

Pinnipeds have streamlined bodies, rounded in the middle and tapered at the ends, with a thick layer of fat beneath the skin. Their limbs are short and their feet are long and webbed, forming flippers. The sea lions and fur seals (family Otariidae) and the walrus (family Odobenidae) are able to turn their hind flippers forward for walking on land; they swim chiefly by a rowing action of the long front flippers. The true seals (family Phocidae) are unable to rotate the hind flippers. They progress on land by wriggling on their bellies, pulling themselves with the short front flippers; in the water they are propelled by a side-to-side sweeping action of the hind flippers.

Nearly all pinnipeds are marine, and most inhabit cold or temperate regions. Some spend most of the year in the open ocean, while others inhabit coastal waters and spend varying amounts of time on shores, islands, or ice floes. Occasionally they ascend rivers. All pinnipeds leave the water at least once a year, at breeding time. In nearly all species the females give birth a year after mating, so that the births take place on land, just before breeding begins. The pups are nursed during the period, usually of several months duration, spent on land. Some species spend most of the year far from their breeding grounds; the northern fur seals make particularly lengthy migrations each year. Most pinnipeds have diets of fish and shellfish; many are bottom feeders, with physiological adaptations for deep diving. They have acute hearing and some, if not all, make use of echolocation (sonar) for underwater navigation.

True Seals

True seals are called earless seals because they lack external ear projections; they have functional inner ears. They have short, coarse hair, usually with a close, dense undercoat. Their color and pattern vary with the species; many are spotted. The pups of most species have fluffy coats of a light color. True seals are generally polygamous and gregarious, but most do not form harems at breeding time, as do the eared seals. Some species have definite migrations, but in most the seals spread out after breeding, singly or in groups, over a wide area of ocean. Some polar species migrate in winter to avoid the advancing ice; members of other species winter under the ice, surfacing through holes to breathe.

Most true seal species fall into one of three geographical groups: northern, antarctic, and warm-water species. Nearly all are marine, but the Baykal seal (Pusa siberica) is confined to the freshwater Lake Baykal of Siberia, and the Caspian seal (P. caspica) to the brackish Caspian Sea. In addition several populations of the normally marine harbor seals and ringed seals are found in freshwater lakes. The northern seals include two species of temperate coastal waters: the common seal, or harbor seal, of the N Atlantic and N Pacific, and the larger gray seal of the N Atlantic. The former is the only seal frequently seen off U.S. coasts. The Greenland seal, or harp seal, is found in the arctic Atlantic; the ribbon seal in the arctic Pacific. The small ringed seal and the larger bearded seal are circumpolar arctic species. Antarctic seals include the voracious leopard seal, which feeds on penguins and other sea birds, and the Ross, Weddell, and crabeater seals. The warm-water seals are the Mediterranean, Caribbean, and Hawaiian species of monk seal. A fourth group includes the elephant seal and hooded seal. There are two elephant seal species, one of the Northern and one of the Southern Hemisphere. They are distinguished by their immense size and trunklike snouts. The hooded seal, distinguished by an inflatable bladder over the snout, is found in the arctic Atlantic.

Sealing

Seals have been used by the Eskimo and other northern hunting peoples for food, oil, and hides. Commercial sealing has been largely confined to a few species, most notably the fur seal. Commercially important species of true seals are the harp seal, whose pups are valued for their fluffy white coats, and the ringed seal. The hunting of these seals is regulated by international treaties, and they are not in danger of extinction. The elephant seals were formerly hunted for oil and almost exterminated, but they are now protected and are stabilized or increasing in numbers. The monk seals have been greatly depleted by hunting in past centuries and their survival is threatened, although they are no longer of commercial importance. The Caribbean monk seal is believed by some authorities to be extinct. The ribbon seal and Ross seal are not much hunted; estimates of their populations have varied considerably, but they are not thought to be endangered.

Classification

Seals are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Carnivora, suborder Pinnipedia.

Bibliography

See B. Davies, Savage Luxury: The Slaughter of the Baby Seals (1971); V. B. Scheffer, The Year of the Seal (1972); J. E. King, Seals of the World (2d ed. 1983); R. L. Gentry and E. L. Kooyman, Fur Seals (1986).

seal, stamp made from a die or matrix of metal, a gem, or other hard substance that yields an impression on wax or other soft substance. The use of seals is very ancient, examples of great antiquity occurring in China, Egypt, Greece, Rome, and other places. The most common form was the seal ring, of which the gem formed the seal. Ecclesiastical seals, used in the 9th cent., reached their highest perfection in the 13th and 14th cent. The use of seals with emblematic designs antedates the development of the escutcheon and is therefore important in the history of heraldry. Edward the Confessor was the first English king to adopt a Great Seal for the kingdom. Heraldic or emblematic seals are in wide use by national, state, and local authorities, by institutions of all kinds, and in the certification of legal documents. A committee was appointed by the Continental Congress on July 4, 1776, to prepare a device for the Great Seal of the United States (see United States, Great Seal of the).

Nonmigratory, earless seal (Phoca vitulina) found throughout the Northern Hemisphere. Harbour seals are whitish or grayish at birth, generally gray with black spots as adults. The adult male may reach a length of about 6 ft (1.8 m) and a weight of almost 300 lb (130 kg); the female is somewhat smaller. Found along coastlines and in a few freshwater lakes in Canada and Alaska, the harbour seal is a gregarious animal that feeds on fish, squid, and crustaceans. It is of little economic value and in some areas is considered a nuisance by fishermen.

Learn more about harbour seal with a free trial on Britannica.com.

Aquatic carnivore with webbed flippers and a streamlined body. Earless (true, or hair) seals (of the family Phocidae, with 18 species) lack external ears. In water, they propel themselves by side-to-side strokes of the hind limbs and maneuver with their forelimbs. On land, they wriggle on their belly or pull themselves with their forelimbs. Earless species include the elephant seal, harbour seal, harp seal, and leopard seal. The eared seals (family Otariidae, with five species of sea lion and nine of fur seal) have external ears and longer flippers. In water, they propel themselves by a rowing motion of their forelimbs; on land, they use all four limbs to move about.

Learn more about seal with a free trial on Britannica.com.

or sea leopard

Species (Hydrurga leptonyx) of generally solitary earless seal (family Phocidae) found in Antarctic and sub-Antarctic regions. It is the only seal that feeds on penguins, young seals, and other warm-blooded prey. It is slender and has a long head and long three-cusped cheek teeth. Named for its black-spotted gray coat, it attains a maximum length and weight (greater in the female) of about 12 ft (3.5 m) and 840 lbs (380 kg). It has a reputation for ferocity but is not known to make unprovoked attacks on humans.

Learn more about leopard seal with a free trial on Britannica.com.

Migratory earless seal (Pagophilus groenlandicus, sometimes Phoca groenlandica) of the North Atlantic and Arctic oceans. The adult male is light grayish or yellowish, with brown or black on the head and a similarly coloured U-shaped marking on the back and sides. The female is less clearly marked. Adults are about 6 ft (1.8 m) long and typically weigh between 265 and 300 lbs (120 and 135 kg). Harp seals feed on fish and crustaceans and spend much of the year at sea. They breed near Newfoundland, Can., and in the Greenland and White seas. Until two weeks old, the pups bear a fluffy white coat highly valued by the fur trade; public indignation over hunting methods (including clubbing) has led to increased regulation and supervision of sealing activities in the Newfoundland area.

Learn more about harp seal with a free trial on Britannica.com.

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.

Learn more about fur seal with a free trial on Britannica.com.

Elephant seal bull (Mirounga)

Either of the two largest pinniped species: the northern elephant seal (Mirounga angustirostris), of coastal islands off California and Baja California, or the southern elephant seal (M. leonina), of sub-Antarctic regions. Both are gregarious earless seals. The male has an inflatable, trunklike snout. The northern species is yellowish or gray-brown, the southern species blue-gray. Males of both species reach a length of about 21 ft (6.5 m) and a weight of about 7,780 lbs (3,530 kg) and are much larger than the females. Elephant seals feed on fish and squid or other cephalopods. During the breeding season, bulls fight to establish territories along beaches and to acquire harems of up to 40 cows.

Learn more about elephant seal with a free trial on Britannica.com.

Small stone cylinder engraved in intaglio on its surface to leave impressions when rolled on wet clay. It first appeared circa 3400–2900 BC and is considered to be one of the finest artistic achievements of Mesopotamia. The earliest examples used geometric or animal patterns; later seals incorporated the owner's name and depicted a variety of motifs. They were used to mark personal property and make documents legally binding. The seals were adopted in Egypt and the Indus civilization.

Learn more about cylinder seal with a free trial on Britannica.com.

Any of about 25 species of herbaceous perennials that make up the genus Polygonatum (lily family), found throughout the Northern Hemisphere. Particularly common in the eastern U.S. and Canada, Solomon's seals flourish in damp, wooded areas and thickets. They have thick, creeping rhizomes and tall, drooping stems, and they bear clusters of white or greenish-white flowers in the axils of leaves, followed by drooping red berries. Similar plants of the genus Smilacina, known as false Solomon's seal, bear their flower clusters at the tips of the stems.

Learn more about Solomon's seal with a free trial on Britannica.com.

Seal may refer to:

Legal

  • Seal (contract law), a legal formality for contracts and other instruments
  • Seal (device), an official stamp or symbol used as a means of authentication
  • Seal (Chinese), a stamp used in East Asia as a form of a signature
  • Cylinder seal, an engraved cylinder used to roll an impression onto a flat surface, such as clay
  • Record sealing, the practice of sealing or destroying court records

Biology

Naval and scouting

People

Places

Religion

Science and Technology

See also

Search another word or see sealon Dictionary | Thesaurus |Spanish
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature
FAVORITES
RECENT

;