Popular Science Monthly/Volume 14/March 1879/The Aard-Vark or Earth-Hog
IN the class Mammalia the order Edentata is one which offers a very great diversity. To judge from their name, the Edentates should all be animals without teeth; yet, though some of them, as the ant-eater and pangolin, offer this peculiarity, others, on the contrary, as the sloth, the armadillo, and the orycteropus or earth-hog, have the jaws provided with organs of mastication, except the portion where the incisors should be. Again, the nails which terminate the digits of the Edentata are sometimes sharp and hooked, so that the animal may climb easily and suspend itself from the branches of trees; again, they are spade-shaped, so that the animal may excavate the ground. Finally, while in some the integument is reënforced by bony concretions, in others it is covered with imbricate scales, in others clothed with coarse hairs, and in others still perfectly nude. From all this it results that naturalists are greatly puzzled when they have to name the general characteristics of the order. Nevertheless, it may be said that these mammals bear in their skeleton and in the arrangement of their viscera certain signs of inferiority; that their salivary glands are highly developed, a fact accounted for by their insectivorous diet; and that in their circulatory system they present some peculiar features, certain interlacings of the blood-vessels which regulate the flow of the blood to the limbs, which latter usually move with extreme slowness. Furthermore, it may be added that, in Edentata with teeth, those organs have a peculiar aspect, being for the most part void of enamel, and, to all appearance, consisting of a number of cylinders standing side by side.
In the animal world as at present constituted the Edentata are all of medium or even small size; but in former geological epochs they attained very considerable dimensions, rivaling even the elephant. The megatherium, whose bones have been found in Buenos Ayres, was 42 metres (144 feet) in length, and 22 metres (64 feet) in height; and the megalonyx and the mylodon, found in the same locality, were also of gigantic proportions. And it is curious to observe that America, where the remains of these great creatures are found, is still the continent which possesses the greatest abundance of animals belonging to this order. The Old World, on the other hand, possesses only a few species, and Australia none at all, the part of the Edentata being in that strange country played by the Monotremata, Echidna, and Ornithorhynchi.
Some species of the Edentata are well known to our readers. The armadillo and the pangolin are common in our zoölogical gardens; the ant-eater and the sloth are to be seen there too, though far more rarely. But besides these familiar species, there are others which, till recent times, were all unknown in menageries, and of which but a very imperfect idea could be formed from the stuffed specimens in the public collections. To this class belongs especially the orycteropus, or earth-hog, a curious sort of Edentate from tropical Africa, which several travelers, and among them Von Heuglin, had vainly tried to carry to Europe alive. Two or three months ago, however, the Paris Museum of Natural History was so fortunate as to secure an animal of this genus. It is quartered in the monkey-house, sheltered from the cold, and there, no doubt, it will be able to live for some time to come in captivity.
The traveler Kolbe, about the middle of the eighteenth century, was the first to publish some notices of the orycteropus, already known even at that time to the Dutch settlers under the name of aard-vark (earth-hog); a little later Camper procured the skull of one of these animals, and studied its osteological character; but to Étienne Geoffroy Saint-Hilaire belongs the credit of having clearly pointed out the essential differences which distinguish the orycteropi from the ant-eaters of the American Continent.
The specimens in our museums and the engravings hitherto published in works of natural history give a very imperfect idea of the orycteropus. In the stuffed specimens—the only models the designer
had at his command—the skin was greatly distended, and the body was disproportionately long. As will be seen from the accompanying figure, drawn from life, the orycteropus is, on the contrary, of heavy build, with arched back, like a pig, which animal it further resembles in that its skin is sparsely strewed with hairs. But its very long ears, instead of being pendent like those of the pig, rise like horns on both sides of the head; neither is the tail slender or twisted into a corkscrew curl; on the contrary, it is of conical shape and very thick at the base. Finally, the rather elongated head, terminating in a regular snout, has at its extremity a buccal opening rather larger than in the ant-eater, but yet far smaller than in swine. The teeth, numbering five or six pairs in the lower jaw and six or seven in the upper, increase in size from the first to the one before the last on each side. Their structure is peculiar, being far less dense than in most Mammalia, and having no coating of enamel. The grinding surface is flattened, and the single root is pierced with a number of holes in its periphery. The slender, protractile tongue is, as in nearly all of the Edentata, covered with a viscous substance designed to secure the small insects on which the animal lives. The short, heavy feet terminate, the anterior in four digits, the posterior in five, all armed with strong, hoof-like claws. In the posterior feet, as in the anterior, the external lateral digits are a little shorter than the others.
The family Orycteropidæ comprises only a single genus, in which we can, not without much difficulty, distinguish three species, viz.: the Cape orycteropus or earth-hog, the one first known; the orycteropus of Senegambia, described by Lesson; and the orycteropus of Ethiopia, studied by D'Abbadie and D'Arnaud on the banks of the White Nile. These three species are identical in their habits, of nearly the same size, 1·3 metre (about 52 feet) from the snout to the extremity of the skin, and of the same general form; they differ only in the proportions of the cranium and of the limbs, and in the color and appearance of the skin. Thus, in the Cape orycteropus, for instance, the surface of the body presents a scanty covering of straight, soft hairs, which are shorter on the back than on the belly. In the orycteropus of Ethiopia, on the other hand, the skin is almost perfectly nude, with merely a few straggling, brownish hairs on the ears, the tail, and the base of the limbs. To this species belongs the individual recently acquired for the Jardin des Plantes, and of which our figure is a faithful portrait. It will be seen that the body is swollen like a full skin-bottle, and furrowed with creases which radiate from the abdominal region between the paws. The latter are of enormous size, and the tail, which is soft and flabby, falls to the ground by its own weight. The general appearance of the animal is at once mean and grotesque. Looked at from behind, it resembles a bag, the long ears projecting on each side being the ends of the string by which the mouth of the bag is tied.
This orycteropus lives in pairs in the plains of Kordofan, where it is called by the Arabs abudelatif, i. e., "the father that owns claws." In the daytime it lies hidden and doubled up in a deep hole, which it digs in the loose soil of the plain by means of its broad, sharp claws. Toward evening it quits this hiding-place and begins to move about, advancing either by leaps, or else with an unsteady gait, walking nearly always on the extremities of its digits. Whatever may have been written heretofore by naturalists, the orycteropus is in fact digitigrade rather than plantigrade. When the animal is walking the head is inclined, the snout nearly touching the ground, the ears laid half-way back, and the tail trailing. From time to time the animal stops to listen: it is guided principally by hearing and smell, and by the same means contrives to escape from its enemies. On finding a path that has been traveled over by ants or termites, it follows it up to the ant-hill; having reached the latter, it attacks the structure with its paws, making the dust fly all around, and digging rapidly till it comes to the center, or at least to one of the principal streets. Then, alternately exserting and retracting its viscous tongue, it devours the ants by the thousands. Having made an end of one nest it attacks another, and so on till its hunger is appeased. When we consider the alarming rate at which ants and termites multiply, and the damage they cause, we must recognize in the orycteropus one of the most efficient of man's auxiliaries in tropical regions.
The orycteropi are extremely timid: at the slightest noise they try to get underground. If they find no suitable hole or crevice, then they quickly dig for themselves a hiding-place. The late J. Verreaux, who had many a time observed orycteropi at the Cape, has told me of how, having once seized by the tail one of them when it had got but half of its body underground, he could not get the animal out except by having the ground dug to a considerable depth. In eastern Africa the negroes, approaching cautiously, kill the orycteropus by a sudden thrust of a lance before it has time to disappear. In Senegal, on the other hand, the animal is caught in iron traps, or hunted with dogs by night. The skin of the animal is thick, and makes good, strong leather. The flesh is by some travelers described as juicy, with a taste like that of pork; according to others it is disgusting, being strongly impregnated with ant-odor. Levaillant could never bring himself to eat of it.
In captivity the orycteropus seems stupid, passing most of the day in sleep, rolled up into a shapeless mass. The individual at the Jardin des Plantes, since winter came in, never quits its nest till about five or six o'clock in the evening. Then it begins to roam about its quarters, returning constantly to the stove, where it warms itself with evident pleasure while it squats on its hind legs and keeps its snout steadily pointed at the fire.
- Translated from "La Nature," by J. Fitzgerald, A.M.