The Cambridge Natural History Part 36

FIG. 224.--Himalayan Bear. _Ursus tibeta.n.u.s._ 1/15.

A very large number of species of Bears have been described. But it is the opinion of Mr. Lydekker[314] and of others that many of these are really to be referred to the European Brown Bear; in this event the Grizzly of North America, the Isabelline Bear, the Syrian Bear, a Bear from Algeria, the Kamschatkan and j.a.panese Bears, besides the extinct _Ursus fossilis_ of Pleistocene caves, are to be regarded as slight modifications of _Ursus arctos_. On the other hand, the great Cave Bear, _U. spelaeus_, {443} and the Thibetan Blue Bear (_U. pruinosus_) are distinct species, not to be confounded with _U. arctos_. Neither, of course, are the Peruvian _U.

ornatus_ and the Sun Bear, _U. malaya.n.u.s_.

[Ill.u.s.tration]

FIG. 225.--Malayan Bear. _Ursus malaya.n.u.s._ 1/12.

The Polar Bear has even been placed in a separate genus, _Thala.s.sarctos_, a proceeding which is quite unnecessary. The white colour of this Bear tends to become browner with age. It is one of the few mammals which extend right round the pole; the Polar Bear is of course a purely Arctic animal. The chief food of the Polar Bear is Seal. Out of thirty Bears examined, Mr.

Koettlitz found that only fifteen had animal remains in their stomachs, and these remains were invariably Seal. The animal apparently hunts by scent rather than by sight or hearing, both of which senses seem to be somewhat dull. The males and females wander separately, except of course during the breeding season. The Bears dig holes in which they may remain for some time, but there is no hibernation. In Pleistocene times, the Polar Bear extended as far south as Hamburg. The female has four mammae, pectoral in position.

_Melursus_ includes only _M. l.a.b.i.atus_, the Sloth Bear of India. This animal has an upturned snout, which is described as closely resembling that of _Mydaus_, the Teledu. The snout has no groove. {444} All Bears are largely vegetarian and insect feeders; but this Bear is especially so. It delights in the nests of Termites, and its energy in destroying these hills for the sake of their inhabitants is so great that the name of "sloth"

appeared to Sir Samuel Baker to be an entire misnomer.

_Aeluropus_, a rare Carnivore with but one species, _A. melanoleucus_, is not inferior in size to the Brown Bear, and is distinguished by its largely white coloration. It was discovered in the mountains of East Thibet by Pere David, and described by Milne-Edwards[315] as a distinct and new genus, the discoverer himself having named it as a species of _Ursus_. It is a vegetable-feeding creature and bulky in form, with a rudimentary tail and a short broad head; in fact, more like a Bear than a Procyonid (with which group it is placed by some). The width of the head, however, is greater than in any other Carnivore; it is most closely approached in this by _Aelurus_ and by _Hyaena_. The molar formula is Pm 4/3 M 2/3. The soles are hairy. There is no alisphenoid ca.n.a.l. The molars are especially large and multicuspid.

[Ill.u.s.tration]

FIG. 226.--_Aeluropus melanoleucus._ 1/12.

FOSSIL URSIDAE.--The genus _Ursus_ itself goes back to Pliocene times. The well-known Cave Bear, _Ursus spelaeus_ of {445} Pleistocene times, was one of the commonest of Carnivorous creatures during the very early times of the present era. It was as huge as a Polar Bear or a Grizzly. The skull is remarkable for the fact that the first three premolars, which are small in all Bears, dropped out early in life. An immense number of names have been given to what are in all probability the same species as this Cave Bear of remote antiquity.

_Hyaenarctos_ is the oldest genus of true Ursidae. It goes back into Middle Miocene times, and ranged over Europe and North Africa.

_Arctotherium_ is an American genus of Pleistocene times. The likeness of some of the extinct Canidae to Bears has been already commented upon.

{446}

CHAPTER XIV

CARNIVORA (_CONTINUED_)--PINNIPEDIA (SEALS AND WALRUSES)--CREODONTA

SUB-ORDER 2. PINNIPEDIA

This group includes the Seals, Sea-Lions, and Walruses,[316] all aquatic and, for the larger part, marine creatures. Being aquatic they have to some extent acquired a fish-like form, though not so completely as have the Whales and even the Sirenia. This is most complete so far as the group is concerned in the Seals, where the hind-limbs have become soldered to the tail and are inefficient as walking legs, where the external ears have vanished, and where the general shape of the body is tapering and thus fish-like. The Walruses and Sea-Lions are less modified in this direction; in the latter (not in the former) the external ear, though small, is persistent, and the hind-limbs are capable of being used as organs of progression upon dry land. The general characters applicable to the Carnivora, given upon a previous page, apply to the Pinnipedia.

[Ill.u.s.tration]

FIG. 227.--Skeleton of Seal. _Phoca vitulina._ (After de Blainville.)

The characters confined to the Pinnipedia as a whole are mainly these:--The greater part of the limbs are enclosed within the skin, the hands and feet are fully webbed, and there is a tendency for the nails to disappear, and for the phalanges to increase in number--characters which are clearly not diagnostic of the order but correlated with an aquatic life, since they reappear, and are indeed exaggerated, in the Cetacea. The teeth are peculiar in that the milk dent.i.tion is feeble and is early shed. This, as it were, undue emphasis upon one of the two sets of teeth is another likeness to the Whales, {447} where, however, it is the milk dent.i.tion that is most p.r.o.nounced, the "permanent" being feeble and very early shed. But the dent.i.tion of the Pinnipedes presents other likenesses to the Cetacea, which are, it must be remembered, regarded by some as a modification of the Carnivorous stock, in which case, of course, the likenesses may be genetic rather than due to adaptation in the two cases. There is a distinct tendency towards a h.o.m.odont series, the grinding teeth being often very simple, and the very distinct carna.s.sial tooth of many terrestrial Carnivores being absent. Finally, the number of the back teeth shows some signs of being on the increase; and Professor Kukenthal has found that this increase is due to the division of existing teeth. Here is a point of likeness to the many teeth of the typical Toothed Whales. Dr. Nehring found in several examples of _Halich.o.e.rus grypus_ the normal five back teeth increased to {448} six, and the additional molar was at the end of the series, thus suggesting a lengthening of jaw coupled with an increase in number of teeth.

The incisor teeth of the Pinnipedia differ from those of the land Carnivora in that there are nearly always fewer than 3/3, at least in the adult animal. In possessing lobulated kidneys the Pinnipedia differ from all terrestrial Carnivores except the Otters and Bears--a significant fact.

In the characters of the skeleton the Pinnipedia show many peculiarities.

The cranial part of the skull is proportionately to the facial part greater than in terrestrial Carnivora; there is no lachrymal bone, and the orbit is to some extent defective in ossification. The alisphenoid ca.n.a.l, so important a feature in the Carnivora, may be present or absent. It is present, for example, in _Otaria jubata_.[317] This genus also has the more primitive small and rugged tympanic bullae, which are inflated and more Cat-like in others. The vertebrae show an interesting Creodont peculiarity in the complex interlocking arrangements of the zygapophyses of the dorsal vertebrae. The ossicula auditus differ from those of their terrestrial allies in their large size and ma.s.sive growth. In this they have come to be like those of the Whales and Sirenians.

[Ill.u.s.tration]

FIG. 228.--Patagonian Sea-Lion. _Otaria jubata._ 1/20.

There is no doubt about their close resemblance to the {449} terrestrial Carnivora, but the question is, to which group of Carnivora have they the most likeness. The semiaquatic Otter, and the still more thoroughly aquatic (marine) _Enhydris_, suggest an affinity in that direction. The long body and short legs of the Otter, which is more thoroughly at home pursuing fish in the streams than in waddling clumsily upon the banks of the streams, seem to require but little external change to convert it into a small Seal, while the long and completely webbed hind digits of _Enhydris_ are even more like those of a Pinniped. The Sea-Lions, in which the external ear has been preserved, and in which the limbs have not become so entirely useless for progression on the land as they have in the Seals, seem to be the intermediate step in the evolution of the latter. This, however, is not the opinion of Dr. Mivart, who, without definitely committing himself on the point, presents some evidence for the a.s.sumption that the marine Carnivora are diphyletic. This double origin, however, is not from two groups of the terrestrial Carnivora. Dr. Mivart, in common with many others, holds that the Pinnipedia as a whole are undoubtedly nearer to the Arctoidea than to either of the two remaining sections of the sub-order. One of the most striking structural characters in which they show this resemblance is the brain; the peculiar Ursine lozenge, already treated of as so distinctive a character of the Arctoidea, is repeated in the Pinnipedia.

There are, however, other points of likeness which seem rather to point to a Creodont origin. _Patriofelis_ is a genus that from more than one side may be looked upon as a possible ancestor of these animals. The Creodont peculiarity of the vertebrae has already been referred to. It may be added that the facial part of the skull is small in _Patriofelis_, which appears, moreover, to have had an alisphenoid ca.n.a.l. A very remarkable resemblance lies in the structure of the astragalus. This is not deeply grooved on the tibial facet as it is in Fissiped Carnivora. This might be held to be an instance of degeneration in the aquatic Seals, which do not use their limbs as walking organs. But Professor Wortman[318] has pointed out that in the Sea-Otter, which is entirely aquatic, the groove exists and is plain. The likeness offered to the Seals by the spreading feet of _Patriofelis_ is noticed under the description of that genus.[319]

{450}

[Ill.u.s.tration]

FIG. 229.--Cape Sea-Lion. _Otaria pusilla._ 1/16.

FAM. 1. OTARIIDAE.--The family Otariidae[320] is no doubt the least modified of the aquatic Carnivora. It is rational, therefore, to commence the survey of the group with this family. They have preserved, as already noted, the independence of the hind-limbs; the external ear is present, though small; there is an obvious neck, and the nostrils are at the end of the snout, as in terrestrial creatures generally. The nails are small and rudimentary, save those upon the three middle digits of the foot. It is a singular fact that among the Otaries the angle of the lower jaw is "inflected as much as in any Marsupial." The literature relating to this family is great, and it seems difficult to reconcile the very varying opinions as to how many genera ought to be admitted. Mr. Allen arranged the nine species which he allowed {451} in six genera; but more generic names have been proposed. At the other extreme stands Dr. Mivart, who speaks of only one genus, _Otaria_; of this genus the number of species is by no means agreed upon. There can, however, be no doubt of the distinctness of the Northern Fur Seal, _O. ursina_ (the "Seal" of commerce and the cause of international complications), of the Patagonian Maned Sea-Lion, _O.

jubata_,[321] of _O. pusilla_ of the Cape, of the Californian _O.

gillespiei_, of _O. hookeri_ from the Auckland Islands, and of four or five others. The range of the genus is wide, but is mainly Antarctic. It is usual to speak of "Hair Seals" and "Fur Seals," the latter being the species which produce the "sealskin" of commerce. The difference is that in the Fur Seals there is a dense, soft under-fur, which is wanting in the other group. It is, however, impossible to make this character the basis of a generic subdivision. There is a Fur Seal, _O. nigrescens_, in South America as well as the more widely-known northern form.

FAM. 2. TRICHECHIDAE.--This family contains but one genus, _Trichechus_, the Walrus or Morse, or _Odobaenus_, as the more correct term seems to be.

It is a tiresome result of accurate conformity with the rules of priority in nomenclature that the name _Trichechus_ should be applied to the Manatee. There is but one species of Walrus, though it has been attempted to show that the Pacific and Eastern forms are different. The animal is Arctic and circ.u.mpolar. The Walrus is characterised by the enormous canines of its upper jaw, which form the well-known tusks and reach a length of 30 inches. The animal can progress on land like the Sea-Lions; but, as in the Seals, there are no external ears, though there is a slight protuberance above the meatus auditorius. The strong bristles upon the upper lip are as thick as crow quills. The pectoral limb has nails, but these are small, as in the Sea-Lions. The under surface of the ma.n.u.s has a warty pad, which cannot but a.s.sist[322] in maintaining a foothold upon slippery ice. The hind-limbs have longer nails, which are still diminutive and subequal in size. There is no free tail. The liver of this animal is much furrowed, but not so much so as in _Otaria_, though more so than in _Phoca_. The kidneys are of course lobulate, as in the other aquatic Carnivores. The milk dental formula appears to be I 3/3 C 1/1 Pm + M 5/4. In the adult the formula[323]

is I 1/0 C 1/1 M 3/3.

{452}

[Ill.u.s.tration]

FIG. 230.--Common Seal. _Phoca vitulina._ 1/8. (From Parker and Haswell's _Zoology_.)

FAM. 3. PHOCIDAE.--The true Seals have no external ears, and the nostrils are quite dorsal in position as in other aquatic animals, such as the Crocodile. There is obviously an approach to the conditions characteristic of the Whales. The hind-limbs are useless for locomotion on land. They are bound up with the tail, and form functionally merely a part of the tail. In this family there are, at any rate, eight genera.

_Phoca_ and _Halich.o.e.rus_ are not very wide apart from each other. In both there are five well-developed claws on feet and hands. They are British, and generally Arctic and temperate in range. For some reason or other the late Dr. Gray placed _Halich.o.e.rus_ in the same sub-family with the Walrus!

_Phoca_ is not only marine, but is found in the Caspian and in Lake Baikal.

Their existence in those inland seas is believed to be a vestige of a former connexion with the sea. _Halich.o.e.rus grypus_ is a large seal 8 feet in length when full grown. Its colour is yellowish grey, with darker grey spots and blotches. It is not uncommon on the sh.o.r.es of our islands, particularly of the Hebrides and Argylls.h.i.+re. The commonest Seal is _Phoca vitulina_, not more than 4 to 5 feet long, and of the same spotted coloration as the last. This Seal has, however, a much wider distribution, being Arctic as well as British, American, and North Pacific. A curious fact about this Seal is that it is not impatient of fresh water; not only will it ascend rivers, but it will live in inland lakes. It is said to be especially sensitive to musical sounds. _P. hispida_ is British, but a rare visitor to our islands. It is essentially an Arctic species. The Harp Seal, _P. groenlandica_, is so called on account of a harp-shaped black bar in the males, which starts at {453} the shoulders and extends to the thighs.

Like the other Seals mentioned, the young are white when first born. As may be inferred from its scientific name this species is also Arctic in range.

It is also a rare visitor to these sh.o.r.es.

The genus _Cystophora_ is the only other genus of which there is a British representative. It is called the Hooded Seal on account of an inflatable sac upon the face, with which it is said to attempt to terrify its enemies.

The genus has an incisor less in each half of each jaw than _Phoca_ and _Halich.o.e.rus_. Its formula is I 2/1 while these genera are both 3/2. _C.

cristata_ is a large species reaching a length of 10 feet. The colour of the back is dark grey with deeper coloured spots. A few individuals only have been recorded from our coasts.

_Stenorhynchus_ ( = _Ogmorhinus_) is an Antarctic genus. The hind-feet are clawless. The incisors are 2/2. The molars have an additional cusp, _i.e._ three in all.

The genus _Leptonyx_ with but one species, _L. weddelli_, is purely Antarctic in range. Like the last genus it has two incisors, and has but rudimentary claws upon the hind-feet; the first and fifth toes moreover are the longest. The genus chiefly differs from the last in the simple conical crowns of the molars, which have not the additional cusps of _Stenorhynchus_.

_Ommatophoca_ is another Antarctic genus with but a single species, _O.

rossi_. In this genus the hind-feet have no claws, and the first and fifth toes are longer than the others. The claws of the fore-feet are rudimentary. The immense size of the orbits gives the name to the genus.

There are two incisors, and the molars are all very small.