ZEBRAS, asses and horses are descended from very distant types in which all four legs possessed extremities with five fingers or toes, the whole hand or foot being placed flat on the ground in walking. Gradually the ancestors of the horse came to walk on the ends of the fingers or toes, so that, in the course of a very long time, the middle finger or toe became greatly enlarged, its nail forming the hoof, while the other digits disappeared.
The domestic horse is distinguished from asses, quaggas and zebras by having relatively smaller ears, a more abundant tail, and usually the presence of bare warty patches on the inner side of all four legs. The wild asses of Africa would seem to have been the ancestors of the domestic ass, and one of them, the Somali wild ass, is the finest example of his race. In his case, the stripe on the back and shoulders, so distinctive of all asses, is less noticeable, though the striping on the legs is well marked.
Zebras approach more nearly to asses than to horses. In both, the mane is erect, the upper part of the tail is free from long hairs, and there are warty patches on the fore-legs only. The ears are longer, the head relatively larger and the hoofs narrower than those of horses. Another marked difference is the striping of the head and body. Many hybrids between various members of this family have been produced, thus showing their affinity and common origin at some not very distant period.
The even-toed ungulates make up the larger half of the order. They include the hippopotamus family, which is not far removed from the pigs. They are bulky mammals, with very long, barrel-shaped bodies, short, massive legs, and enormous mouths. The eyes are small, but projecting, and the nostrils are placed on the highest point of the muzzle, so that
the animal when in the water can breathe without exposing more than a few inches of the head above the surface. These animals are good swimmers and pass the greater part of their life in the water, feeding exclusively on vegetable matter. The pygmy hippopotamus of Liberia is a much smaller animal, about a quarter the size of the other species and less aquatic in its habits.
Pigs are very nearly related to the foregoing family, and occur in almost every part of the globe except Australia. A special characteristic is the presence of an elongated snout, at the end of which are the nostrils. This is of great use to the animal in grubbing up roots, etc., for food. Pigs have a very keen sense of smell, and are used in some parts of the world to hunt for truffles. They will eat anything. Though not always given credit for it, they are intelligent and courageous animals, and if left to themselves would not be the byword for filth that they are.
Notable species are the wild boars of Europe and Asia, the babirussa of Celebes and Borneo, in which the canine teeth pierce the upper lip and curve backwards; the wart-hogs of Africa, distinguished by huge, curly upper tusks and warty growths on the face; and the gigantic black forest hog of the Congo. In the New World, the peccaries are smaller in size, very gregarious, and, in the case of one species at least, credited with a disposition to attack man if molested.
So far all the ungulates considered have been non-ruminants —that is, animals which do not chew the cud. The remainder chew the cud. This means that their stomachs are divided into compartments, into the first of which, known as the paunch, their food passes unchewed. From the paunch it is later returned in small quantities to be chewed while the animal is at rest.
The true camels are found only in Africa and Asia. The Arabian camel has only one hump—the term ‘dromedary ‘being applied to the finer breed of this animal, one more suitable for fast travel. The camel may be said to be a first-rate example of fitness to environment, every part of its body being exceedingly well suited to the regions in which it usually lives. It may be questioned, however, if its proverbial capacity for going without water has not been somewhat exaggerated. The Bactrian camel of Central Asia is a heavier, two-humped animal with long shaggy hair, adapted to withstand considerable cold.
The llamas and alpacas of South America are an allied group, which before the Spanish Conquest were the only domesticated animals in Peru. The llama is used in its native country largely as a beast of burden, as is also the alpaca, though the latter is kept more for its wool, which is longer and more abundant than that of its relative.