The New International Encyclopædia/Seal (mammal)

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The New International Encyclopædia
Seal (mammal)
Edition of 1905. Written by Hubert Lyman ClarkSee also Pinniped on Wikipedia, and the disclaimer.

SEAL (AS. seol, siol, OHG. selah, selach, seal). A carnivorous aquatic mammal of the suborder Pinnipedia, without tusk-like canines in the upper jaw; any pinniped except the walrus. Seals are specially modified for their aquatic life, particularly in the structure of the limbs. The upper arm and forearm of the front limb, and the two corresponding parts of the hind limb, are very short and more or less imbedded in the tissues of the body, while the hands and feet, especially the latter, are greatly enlarged and fully webbed. Five well-developed digits are present in all cases, but in the hind limbs the outer and inner digits are stouter and often longer than the other three. There are no clavicles in the shoulder girdle, and the limbs are poorly adapted for use on land. The tail is always very short, but the hind limbs often serve the purpose of a rudder. The body is sleek and graceful, tapering posteriorly as in cetaceans (q.v.), but the head is always distinct and well formed. The whole surface of the animal develops a hairy covering, even the palms of the hands and soles of the feet being thus protected in the true seals. There are always fewer than twelve incisor teeth, and usually four premolars and only one molar are present on each side of the head, in each jaw. The brain is large and much convoluted, and seals exhibit much intelligence. The eyes are large and exposed, with flat corneas, and external ears, though small, are often present.

Although so specially adapted to their aquatic life, seals come to shore or upon ice-floes to mate and to bring forth their young. One or two young are produced at a time, not oftener than once a year. Seals are polygamous and the males fight savagely for the possession of the females. As the pairing occurs soon after the birth of the young, the latter, known as ‘pups,’ are often neglected and many die. During the breeding season the males do not eat, and it is said they sometimes endure three months of abstinence. The food consists of various marine animals, chiefly fish, squids, and crustaceans; possibly vegetable food is also used at times. It is a curious fact that seals often swallow pebbles and even large stones, which are frequently found in their stomachs, but the purpose is not clearly understood. They are regurgitated, as are also the indigestible parts of the food, such as fish-bones and squids' beaks. Seals are large eaters, the remains of more than 200 squids having been found in a single fur-seal at one time, although digestion is very rapid. The food is masticated little or not at all, fishes being usually bolted head first. In the capture of their food, as in all their movements in the water, seals are quick and graceful. On land, however, their movements are awkward and progression is chiefly effected by a succession of jerks caused by the upward bending and sudden straightening of the spine, which is remarkably flexible, the limbs being little used by the true seals; the eared seals move mainly by the aid of the limbs. Food is not normally taken on land, and in pursuit of it seals are capable of remaining under water for long periods of time, respiration being very slow.

As regards the intelligence of seals there seems to be considerable difference of opinion, according to the opportunities and point of view of the observer. In captivity some species of seal have shown considerable readiness to learn tricks of more or less difficulty, and trained seals have often been exhibited. On the other hand, observations made on the fur-seal in its native haunts seem to show that while the instincts are strong, there is little real intelligence, and ordinarily stupidity is a marked characteristic. The homing instinct is very strong in most seals, and they will return year after year to their breeding grounds, even though they are sure to meet with slaughter. Most species are also very gregarious, and in their herds they constantly tend to imitate each other, so that they follow their leaders in a perfectly unreasoning way.

Seals are widely distributed in all parts of the oceanic world, but especially in the colder regions. A few species occur in the tropics and temperate regions, but it is in the Arctic and Antarctic parts of the ocean that seals really abound. There they swarm on rocky coasts and on ice-floes during the breeding season, and in the water during the rest of the year. Although seals are normally marine, two species inhabit the Caspian Sea and Lake Baikal.


SEALS

NIE 1905 Seal.jpg
COPYRIGHT 1902, BY DODD, MEAD & COMPANY JULIUS BIEN & CO.LITH.N.Y.
1 FUR SEAL — CALLORHINUS URSINUS     3 SEA-ELEPHANT — MACRORHINUS LEONINUS
2 CALIFORNIA SEA LION — ZALOPHUS CALIFORNIANUS 4 WALRUS — TRICHECHUS ROSMARUS


The classification of the seals and the limits of the species are still much debated subjects and are very perplexing. Two principal groups are recognized — true seals (Phoeidæ) and otaries (Otariidæ), the former without external ears, which the latter possess; there are also differences in dentition. The Phoeidæ are all ‘hair’-seals; that is, they have no thick coating of fur under the outer hairy coat. Some of the otaries are also hair-seals, but all fur-seals are otaries. There are three subfamilies of Phoeidæ — Phocinæ, Monachinæ, and Cystophorinæ, the first having ten incisors, the second eight, and the third only six. The Phocinæ include many of the best-known species, such as the common seal (Phoca vitulina), the harp-seal (Phoca Grœnlandica), the floe-rat or ringed seal (Phoca hispida), and the freshwater seals (Phoca Caspica and Sibirica), already referred to.

The common ‘harbor’ seal is circumpolar in its distribution, and extends in range downward into both the North Atlantic and Pacific oceans. It is locally common along the eastern coast of America, and on the wilder and less frequented parts of the British coast. The pelage is yellowish, variously spotted and marked, with brown above, while underneath it is generally yellowish-white; but there is considerable variability in the coloration. In size the common seal is one of the smaller species, the entire length being from three to five feet. Altho\igh gregarious, this species is not found in large ‘rookeries,’ but small herds are occasionally seen. The skin, which is used for leather and other purposes, and the oil, which is colorless, nearly odorless, and in many ways superior to whale oil, are of sufficient commercial importance to subject these animals to continual slaughter, and their numbers are probably steadily diminishing. The females show some attachment to their young, though their devotion has probably been exaggerated. In captivity the common seal is docile and is said to become attached to its keeper. It is endowed with much curiosity, and there may be some basis for the belief that it is strongly attracted by musical sounds. The sense of smell is very acute and the vocal power ranges from a plaintive bleat to a harsh bark or grunt. The popular name ‘sea-calf,’ and the specific name vitulina, have reference to a supposed resemblance between its voice and that of a calf.

The harp-seal is a much larger and more northern species, reaching a length of eight or nine feet and rarely coming south of Newfoundland. It is extremely gregarious and almost wholly pelagic, resorting to the ice-floes only to breed. It is much sought after by sealing vessels, several hundred thousand being annually slaughtered on the breeding grounds. The floe-rat is one of the smallest seals, although about as long as the common species. It is an Arctic form, and is of great importance to the Eskimos as a source of food and clothing. This is the species which forms a domed cavity in the ice, called by the Eskimos an ‘igloo,’ after the name of their own winter houses; and it also keeps open breathing holes through the ice. The seals of the Caspian Sea and Lake Baikal are near relatives to the floe-rat, which they resemble in size, though differing in some other details. Their presence in Lake Baikal, a fresh-water lake, is not so remarkable when one considers that the seal often ascends rivers for long distances and has been taken in Lake Champlain.

The Monachinæ are a small group of half a dozen species, all Antarctic, except the two species of monk-seal which are tropical. The European monk-seal (Monachus albiventris) occurs in the Mediterranean Sea and adjacent parts of the Atlantic Ocean, while a closely ullied species, the West Indian seal (Monachus tropicalis), of which little seems to be known, is confined to the Gulf of Mexico, where it is nearly extirpated. (See Extinct Animals.) These seals have the first and fifth toes of the hind feet greatly longer than the others, and the nails of both fore and hind feet are very small and rudimentary. The other seals of this subfamily are rare and little known except the sea-leopard (q.v.) of the south temperate and Antarctic seas.

The Cystophorinæ are a small group containing only two or three species, but both of the genera are of considerable interest. The hooded seal (q.v.) is a large Polar species, remarkable for the hood-like distensible sac covering the head of the male and connected with the nostrils. The second genus, Macrorhinus, includes the largest of all seals, the elephant-seals (q.v.), or sea-elephants so called in reference to the proboscis of the male as well as the great size.

Turning to the otaries, or ‘eared seals,’ it is convenient to recognize two principal groups, the ‘sea-lions’ or hair-otaries, and the ‘sea-bears’ or fur-otaries. The former group includes the largest species, some of them attaining a length of fourteen feet. The southern sea-lion (Otaria jubata) occurs commonly on the west coast of South America, while the northern sea-lion (Eumetopias Stelleri) is found throughout the North Pacific from California to Japan. The common sea-lion of California is, however, a much smaller species, called the black sea lion (Zalophus Californianus), and is often seen in menageries and zoölogical gardens. It is famous as the attraction at the Seal Rocks, close by the Cliff House, near San Francisco. The sea-lions are all very timid animals, easily terrified, and may be driven in herds, even far inland, by means of flags or umbrellas. See Colored Plate of Seals.

The Fur-Seals. The last group of seals to be considered are the fur-seals, by far the most important commercially of all marine mammals. The fur-seals of the Southern Hemisphere are now usually placed in a separate genus, Arctocephalus, which ranges as far north in the Pacific as Guadaloupe Island (29° N.), although mainly confined to the south-temperate and antarctic zones. The skin is of considerable value, and these seals have therefore been eagerly sought wherever they resorted for breeding. They have therefore been practically, if not totally, exterminated, except in some small rookeries in New Zealand and on the west coast of Cape Colony, which are under rigid governmental control, and yield about 7000 skins per annum: and especially on Lobos Island, off the mouth of the Rio Plata, which is leased by the Government of Uruguay to a private company, which so controls the slaughter that about 13,000 skins are furnished annually.

The northern fur-seals (genus Callorhinus) are confined to the North Pacific Ocean. At the present day they breed mainly on the Pribilof, Commander, Robben, Bering, and Kurile islands, the first being the most famous resort. The northern fur-seal varies considerably in size, color, and proportions, and specialists recognize at least two and perhaps three species. In size the male is very much larger than the female, the difference being especially noticeable in weight. A full grown male is about 80 inches in length and weighs rather less than 400 pounds, while the female is only about 48 inches long and weighs less than 80 pounds. The color is considerably affected by age, the length of time the seal has been out of water, and the amount of dirt on the fur, but in general the adults are dark gray, with a more or less chestnut or seal-brown cast. The young are black above and brownish-gray beneath, but when three months old have assumed the steel-gray pelage of yearlings. At this stage they are nearly white beneath and the sexes are alike. With increased age the white lower parts become grayish; the female assumes the adult aspect a little more slowly. The pelage in all the fur-otaries consists of the ordinary outer coat of ‘water-hair,’ and a dense, soft under fur. To prepare a pelt for use as ‘fur’ the water-hair is removed and the under fur is cleaned. On account of their exceptional warmth, softness, and beauty, sealskins have long been in great demand, and the wanton destruction of breeding females, literally by the millions, in the nineteenth century, so depleted the seal herds that the supply is always less than the demand. The high prices thus constantly obtainable have led to the continued existence of a considerable fleet of vessels which hunt and slaughter seals, wherever they can find them, regardless of age or sex. Ever since the discovery of the Pribilof Islands in 1786, the competition for the skins of the seals breeding there and elsewhere in the North Pacific has been so keen that the animals have been in imminent danger of extermination. The organization of the Russian-American Company in 1799, however, improved conditions somewhat, as the killing of the seals was legally restricted to the employees of a single corporation, which had the greatest interest in the maintenance of the herd. At first the slaughter was indiscriminate as to age or sex, but regulations protecting the females and young were soon made, so that when the Pribilof fur-seal herd came under the control of the United States in 1867, it was in a prosperous condition. Since then it has been sadly depleted. For a discussion of the Alaskan seal question, see Sealing.

The great evil of pelagic sealing lies in the fact that the nursing mothers wander far in search of food, while the males do not take food during the breeding season, but remain on the islands. Consequently practically all the seals taken by pelagic sealers are nursing females, the death of which ordinarily results in the starvation of the pups. There can be no doubt that pelagic sealing is suicidal, the catch showing an annual decrease since 1894, while it is probable that the profits to each vessel engaged in it are extremely small. Recent calculations based on the most trustworthy figures indicate that the Pribilof herd of breeding seals did not in 1903 exceed 60,000 females, and unless remedial measures be devised and enforced the early extinction of the herd is probable.

The terms used in reference to the fur-otaries present a curious anomaly. The animal so generally called ‘fur-seal’ is properly a sea-bear, and very probably more nearly related to the bears than to the true seals. The male is called a ‘bull’ and the female a ‘cow,’ but the young one is a ‘pup,’ which if a male becomes a ‘bachelor.’ The ‘cows,’ moreover, are gathered in ‘harems’ on a ‘rookery’ and, to cap the climax, the capture of these mammals is commonly designated as a ‘fishery’!

For full particulars, in every detail, regarding the fur-seal and the sealing industry, consult the remarkable four volumes issued by the United States Treasury Department in 1899, designated Report of Fur Seal Investigations.