1902 Encyclopedia > Swine

Swine




SWINE. The oldest known even-toed or Artiodactyle Ungulates (see MAMMALIA, vol. xv. p. 429) were neither Oxen, Antelopes, Deer, Camels, nor Pigs, but presented a generalized type, which by modification in various direc-tions has given rise to all these very diverse forms. They were mostly of small size, and had invariably the full number of teeth of the typical mammalian heterodont dentition, viz., 44, of which the incisors were _§ on each side, the canines \, the premolars J, and the true molars §. The molars were short and square, crowned with blunt, rounded cusps, and the canines were not remarkably developed. All the feet terminated in four toes, the two middle ones (the third and fourth of the complete typical mammalian extremity) of nearly equal size, the outer ones (second and fifth) smaller, and also equal. The five-toed ancestor of these forms has not yet been discovered. They had no special weapons, as horns or antlers, on their foreheads. Such was the condition of all the hitherto dis-covered animals of this division at the commencement of the Tertiary period. Very early a change took place in the characters of the molar teeth in certain members of the group : the rounded tubercles became sharp ridges curved in a crescentic form, and better adapted for a purely herbivorous diet, especially for cutting and bruising the comparatively dry and hard blades of grass which grow in open plains. The animals thus separated from the rest —the Selenodont (crescent-toothed) Artiodactyles—have undergone various further modifications of teeth, feet, and other parts, and constitute the diverse forms of ruminating animals mentioned above. Those whose molar teeth retained more of the primitive tuberculated (bunodont) form, were the ancestors of the present family of Swine, some of which, looking upon their organization as a whole, have undergone less change since the Eocene period than almost any other mammals.

Remains of very generalized swine-like animals have been abundantly found in Eocene and early Miocene formations both in America and Europe. In the former continent they never (as far as present evidence indicates) underwent any great diversity of modification, but gradu-ally dwindled away and almost died out, being only represented in the actual fauna by the two closely-allied species of peccary, among the smallest and most insignificant members of the group, which have existed almost unchanged since the Miocene age at least, if the evidence of teeth alone can be trusted. In the Old World, on the other hand, the. swine have played a more important part in recent times, having become widely distributed, and throw-ing off some curiously specialized forms. At the present time, though not very numerous in species, they range through the greater part of the Old World except within or near the Arctic Circle, although, in common with all the other members of the great Ungulate order, they were completely absent from the whole of the Australian region until introduced by man in very recent times.

The existing swine-like animals may be divided naturally into three families :—I. Hippopotamidx; II. Suidx, or true Pigs; III. Dicotylidse, or Peccaries.

I. FAMILY HIPPOPOTAMIDAE.

Muzzle very broad and rounded. Feet short and broad, with four subequal toes, with short rounded hoofs, all reach-ing the ground in walking. Incisors not rooted but con-tinuously growing; those of the upper jaw curved and directed downwards; those of the lower straight and pro-cumbent. Canines very large, curved, continuously growing; upper ones directed downwards. Premolars \; molars f. Stomach complex. Wo csecum.

This appears to be an exclusively Old-World form,—no animals belonging to it, either recent or fossil, having been found in America. The family has been divided into three genera, according to the number of the incisor teeth. (1) Hexaprotodon, incisors f, a type which comes nearest to the generalized or ancestral form of the group, is now extinct, being only known from the early Pliocene formations of the Sub-Himalayan range. (2) Hippopotamus proper, incisors f, contains the one well-known species H. amphibius, now confined to the rivers and lakes of Africa, but formerly (in the Pliocene period) abundantly distrib-uted, under various minor modifications, in Europe, as far north as England. Remains of an allied form have been found in the island of Madagascar, where it is now extinct. (3) Chosropsis, incisors reduced to ^ contains one very small and still little known species, from rivers of Liberia, West Africa, C. liberiensis. See HIPPOPOTAMUS.

II. FAMILY SUIDAE. An elongatea mobile snout, with an expanded, truncated, nearly naked, flat, oval terminal surface in which the nostrils are placed. Feet narrow ; four completely developed toes on each. Hoofs of the two middle toes with their contiguous surfaces flattened. The outer (second and fifth) digits not reaching to the ground in the ordinary walking position. Teeth variable in number, owing to the suppression in some forms of an upper incisor and one or more premolars.

Incisors rooted. Upper canines curving more or less outwards or upwards. Stomach simple, except for a more or less developed pouch near the cardiac orifice. A caecum. Colon spirally coiled. Confined to the Old World.

Sus.—Dentition: if, c{, p%, m%; total 44. Upper incisors diminishing rapidly in size from the first to the third. Lower incisors long, narrow, closely approximated, and almost horizontal in posi-tion, their apices inclining towards the middle line; the second slightly larger than the fir; third much sn

Canines strongly developed and with persistent roots and partial enamel covering, those of the upper jaw not having the usual downward direction, but curving strongly out-wards, upwards, and finally inwards, while those of the lower jaw are directed upwards and outwards with a gentle back-ward curve, their hinder edges working and wearing against the front edges of the upper canines. They appear ex-ternally to the mouth as tusks, the form of the upper lip being modified to allow of their protrusion, but are much less developed in the females than in the males. The teeth of the molar series gradually increase in size and complexity from first to last, and are arranged in con-tiguous series, except that the first lower premolar is separated by an interval from the second. First and second upper premolars with compressed crowns and two roots. The third and fourth have an inner lobe developed on the crown, and an additional pair of roots. The first and second true molars have quadrate crowns, with four principal obtuse conical cusps, around which numerous accessory cusps are clustered. The crown of the third molar is nearly as long (antero-posteriorly) as those of the first and second together, having, in addition to the four principal lobes, a large posterior talon or heel, composed of numerous clustered conical cusps, and supported by several additional roots. The lower molar teeth resemble generally those of the upper jaw, but are narrower. Milk dentition : if, c \, m § ; total 28,—the first permanent premolar having no predecessor in this series. The third incisor, in both upper and lower jaw, is large, developed before the others, and has much the size, form, and direction of the canine. Vertebras: C 7, D 13-14, L 6, S 4, C 20-24. The hairy covering of the body varies much under different conditions of climate, but when best developed, as in the European wild boar, consists of long stiff bristles, mostly abundant on the back and sides, and of a close softer curling under-coat.





This genus occurs at present under three principal modifications or subgenera.

A. Sus proper comprises a number of animals found in a wild state throughout the greater part of Europe (except where exterminated by human agency), the north of Africa, southern continental Asia, and the great islands of the Malayan archipelago, Formosa, and Japan. The following among others have been admitted by zoologists as distinct species :—Sus scrofa, the wild boar of Europe, Asia Minor, and North Africa, once common throughout the British Isles; S. sennaarensis, North-East Africa; S. cristatus, Hin-dustan; S. vittatus, Java, Borneo, Amboyna, Batchian; S. barbatus, Borneo; S. papuensis, New Guinea; S. timorensis, Timor and Botti; S. andamanensis, Andaman Islands ; S. celebensis, Celebes ; S. taivanus, Formosa ; S. leucomystax, Japan; S. verrucosus, Java, Borneo, Ceram. This list will give some idea of the geographical distribution of wild pigs, but it must be borne in mind that through the whole of this region, and in fact now throughout the greater part of the habitable world, pigs are kept by man in a domesticated state, and it is still an open question whether some of the wild pigs of the islands named above may not be local races derived originally from imported domestic specimens. In New Zealand a wild or rather "feral" race is already established, the origin of which is of course quite recent, as it is well ascertained that no animal of the kind ever lived upon the island until after its settlement by Europeans. Whether the various breeds of domestic pigs have been derived from one or several sources is still unknown. As in so many similar cases there is no historic evidence upon the subject, and the researches of naturalists, as Nathusius, Butimeyer, Rolleston, and others, who have endeavoured to settle the question on anatomical evidence, have not led to satisfactory con-clusions. It is, however, tolerably certain that all the species or forms of wild pigs enumerated above and all the domestic races are closely allied, and it is probable (though of this there has been no opportunity of proof)

FIG. 2.—Wild Boar and Young.

will breed freely together. It is a curious circumstance that the young of all the wild kinds of pigs (as far as is known at present) present a uniform coloration, being dark brown with longitudinal stripes of a paler colour, a character which completely disappears after the first few months. On the other hand, this peculiar marking is rarely seen in domestic pigs in any part of the world, although it has been occasionally observed. It is stated by Darwin that the pigs which have run wild in Jamaica and the semiferal pigs of New Granada have resumed this aboriginal character, and produce longitudinally striped young; these must of course be the descendants of do-mestic animals introduced from Europe since the Spanish conquest, as before that time there were no true pigs in the New World. Another character by which the Euro-pean domestic pig differs from any of the wild species is the concave outline of the frontal region of the skull, a form still retained by the feral pigs in New Zealand. B. The diminutive pig of Nepal, the Terai, and Bhutan, Sus salvauius, has been separated from the rest by Hodgson under the generic name of Porcula, but all the alleged distinctive characters prove on more careful investigation to have little real value. Owing to its retired habits, and power of concealment under bushes and long grass in the depths of the great Saul Forest, which is its principal home, very little has been known of this curious little animal, scarcely larger than a hare. The recent acquisition of living specimens in the London Zoological Gardens has, however, afforded opportunities for careful anatomical observation. C. Two well-marked species of African swine have been with more reason separated under the name of Potamochcerus. The dentition differs from that of true Sus, inasmuch as the anterior premolars have a tendency to disappear; sometimes in adult specimens the first upper premolar is retained, but it is usually absent, as well as the first and often the second lower premolars. The molar teeth are also less complex; the last especially has a much less developed heel. There are also characteristic cranial differences. The two species are very distinct in outward appearance and coloration. One is P. africanus, the South African River-Hog, or Bosch-Vark, of a grey colour, and the other P. porcus or penicillatus, the West African Bed River-Hog, remarkable for its vivid colouring and long pencilled ears. It should be noted that the young of both these species, as well as of the pigmy S. salvanius, present the striped character of true Siis, a strong indication of close affinities, whereas in all the following forms this is absent.

Babirussa.—Dentition: i\, c\,p\,m\; total 34. The total number of teeth is therefore considerably reduced, the outer upper incisor and the two anterior premolars of both jaws being absent. The molars, especially the last, are smaller and simpler than in Sus, but the great peculiarity of this genus is the extraordinary development of the canines of the male. These teeth are ever-growing, long, slender, and curved, and entirely without enamel covering. Those of the upper jaw are directed upwards from their base, so that they never enter the mouth, but pierce the skin of the face, resembling horns rather than teeth, and curve backwards, downwards, and finally often forwards again, almost or quite touching the skin of the forehead. There is but one species, B. alfurus, found only in the islands of Celebes and Buru. Its external surface is almost entirely devoid of hair. With regard to the curiously modified dentition, Wallace (Malay Archipelago, i. p. 435) makes the following observations. " It is difficult to understand what can be the use of these horn-like teeth. Some of the old writers supposed that they served as hooks by which the creature could rest its head on a branch.

But the way in which they usually diverge just over anc in front of the eye has suggested the more probable idea, that they serve to guard these organs from thorns and spines while hunting for fallen fruits among the tangled thickets of rattans and other spiny plants. Even this, however, is not satisfactory, for the female, who must seek her food in the same way, does not possess them.

FIG. 3.—Head of Babirussa.

I should be inclined to believe rather that these tusks were once useful, and were then worn down as fast as they grew, but that changed conditions of life have rendered them unnecessary, and they now develop into a monstrous form, just as the incisors of the beaver and rabbit will go on growing if the opposite teeth do not wear them away. In old animals they reach an enormous size, and are generally broken off as if by fighting."

Phacochaerus.—The Wart-Hogs, so called from the large cutaneous lobes projecting from each side of the face, have the teeth still more remarkably modified than in Babirussa. The milk dentition, and even the early con-dition of the permanent dentition, is formed on the same general type as that of Sus, except that certain of the typical teeth are absent, the formula being i\, c\, p>\, m.§, total 34; but as age advances all the teeth have a tendency to disappear, except the canines and the posterior molars, but these, which in some cases are the only teeth left in the jaws, attain an extraordinary development. The upper canines especially are of great size, and curve outwards, forwards, and upwards. Their enamel covering is confined to the apex, and soon wears away. The lower canines are much more slender, but follow the same curve; except on the posterior surface, their crowns are covered with enamel. Unlike those of the babirussa, the canines of the wart-hog are large in both sexes. The third molar tooth of both jaws is of great size, and pre-sents a structure at first sight unlike that of any other mammal, being composed of numerous (22-25) parallel cylinders or columns, each with pulp cavity, dentine, and enamel covering, and packed together with cement. Care-ful examination will, however, show that a similar modi-fication to that which has transformed the comparatively simple molar tooth of the mastodon into the extremely complex grinder of the Indian elephant has served to change the tooth of the common pig into that of Phaco-chcerus. The tubercles which cluster over the surface of the crown of the common pig are elongated and drawn out into the columns of the wart-hog, as the low trans-verse ridges of the mastodon's tooth become the leaf-like plates of the elephant's.

Two species of this genus are distinguished:—P. africanus, Aelian's Wrart-Hog, widely distributed over the continent; and P. xthiopicus, Pallas's Wart-Hog, confined to south-eastern Africa. In the latter species the dentition

reaches its most complete reduction, as in adult specimens the upper incisors are absent and the lower ones worn down to the roots.

III. FAMILY DICOTYLIDAE.

Snout as in Suidae. Dentition : i -§, c y, p _§, m § ; total 38. Incisors rooted; upper canines directed downwards, with sharp cutting hinder edges. Toes, four on the fore feet and three on the hind feet (the fifth wanting). Stomach complex. A cxcum. Confined to the New World.

There is one genus, Dicotyles, with two species, D. tagacu, the Collared Peccary, and D. labiatus, the White-Lipped Peccary. See PECCARY. (W. H. F.)






The above article was written by: Prof. W. H. Flower.



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