HIPPOPOTAMUS, a family (Hippopotamidae) of artio-dactyle ungulate mammals comprising two genera, each containing a single living species. Of these the best known is the hippopotamus [Hippopotamus amphibius), occurring only in Africa, where it abounds in many of the river courses. It is a huge unwieldy creature, measuring in the largest specimens fully 14 feet from the extremity of the upper lip to the tip of the tail, while it ordinarily attains a length of 12 feet, with a height of 5 feet at the shoulders, and a girth round the thickest part of the body almost equal to its length. Its remarkably small ears are exceed-ingly flexible, and are kept in constant motion when the animal is seeking to catch a distant sound. Its eyes are placed high up on the head, and but little below the level of the ears; its gape is wide, and its upper lip thick and bulging so as to cover over even the largest of its teeth when the mouth is closed. It is provided with a consider-able number of molar teeth adapted for grinding vegetable substances, and a formidable array of long spear-like incisors and curved chisel-edged canines or tusks which, according to Baker, root up the rank grass like an agricul-tural implement. Its legs are short, so that the body is but little elevated above the ground; and its feet, which are small in proportion to the size of the animal, terminate in four short toes each bearing a small hoof. With the excep-tion of a few tufts of hair on the lips, on the sides of the head and neck, and at the extremity of the short robust tail, the skin of the hippopotamus, some portions of which are 2 inches in thickness, is entirely destitute of covering. It is usually of a dark fleshy red colour, irregularly marked with blackish spots. The hippopotamus is a gregarious animal, living in herds of from 20 to 40 individuals on the banks and in the beds of rivers, in the neighbourhood of which it most readily finds its appropriate food. This con-sists chiefly of grass and of aquatic plants, of which it con-sumes enormous quantities, the stomach of one of those creatures being capable of containing from 5 to 6 bushels. They feed principally by night, remaining in the water during the day, although in districts where they are little disturbed by man they are less exclusively aquatic, In such remote quarters they put their heads boldly out of the water to blow, but when rendered suspicious by man's persecution, they become exceedingly cautious in this respect, only exposing their nostrils above the water, and even this they prefer doing amid the shelter of water plants. In spite of their enormous size and uncouth form, they are expert swimmers and divers, and can, it is said, remain easily under the water from five to eight minutes. They are also said to walk with considerable rapidity on the bottoms of rivers, beneath at least a foot of water. At night-fall they come on land to feed; and when, as often happens on the banks of the Nile, they reach cultivated ground, they do immense damage to growing crops, destroying by their ponderous tread even more than they devour. To scare away those unwelcome visitors the natives in such districts are in the habit of kindling great fires at night. Although they do not willingly go far from the water on which their very existence depends, occasionally they have been found to travel long distances by night in search of food, and in spite of their clumsy appearance they are able, according to Baker, to climb up steep banks and precipitous ravines with astonishing power and ease. Of a wounded hippopotamus which that traveller once saw leaving the water and galloping inland, he says, " I never could have imagined that so unwieldy an animal could have exhibited such speed. No man could have had a chance of escape." The hippopotamus does not confine itself to rivers only, but when opportunity occurs of exercising choice it has been known to prefer the waters of the ocean as its home during the day. Of a mild and inoffensive disposition, it seeks to avoid collision with man; when wounded, however, or in defence of its young, it is wont to exhibit the greatest ferocity, and the native canoes are frequently capsized and occasionally demolished by its infuriated attacks, its usual bellowing grunt then becoming loud enough to be heard a mile away. As among elephants, so also among hippopotami there are " rogues "_old bulls which, having been expelled from the herd, have become soured in solitude; these are at all times dangerous. Assuming the offensive on every occasion, they attack all and sundry without shadow of provocation; the natives, therefore, are careful to avoid the haunts of those solitaires, which are usually well known.
The rifle of the European has proved the most potent, destroyer of the hippopotamus; but to prove effective it must be aimed at the head, the most vulnerable points in that region being immediately behind the ear and in the eye. Everywhere regarded as a valuable prize, the natives employ a variety of methods in order to secure it, the most common of these being the use of an iron harpoon attached to a line. Allowing themselves to float down stream on a raft, the hippopotamus hunters no sooner reach the sleep-ing herd than the expertest of them plunges his harpoon deep into the body of the selected victim. The light canoes are then launched from the raft, and with all speed the hunters make for the shore, bearing with them the line attached to the harpoon, which they further secure by giv-ing it a turn round the trunk of a tree. Unable to free itself, the hippopotamus wastes its strength in impotent rage, its persecutors meanwhile assailing it with a shower of javelins under which its life blood gradually ebbs away, until at last it is hauled up dead or dying on the shore. Another native method of destroying those animals is by means of a trap known as the " downfall," consisting of a heavy wooden beam armed at one end with a poisoned spear-head and suspended by the other to a forked pole of overhanging branch of a tree. The cord by which the beam is suspended descends to the path beneath, across which it lies in such a manner as to be set free the instant it is touched by the foot of the passing hippopotamus ; the beam thus liberated immediately descends, and the poisoned weapon passes into the head or back of the luckless beast, whose death in the adjacent stream takes place soon after. Such "downfalls" are placed over the paths by which the animals are in the habit of reaching their nightly feeding grounds. They are also occasionally taken by means of ordinary pitfalls, so dexterously concealed as often to entrap the unwary traveller. Although inferior in sagacity to the elephant, the hippopotamus is very far from being stupid, as is frequently proved by its remarkable adroit-ness in the discovery and avoidance of traps and pitfalls, as well as in its timely migration from localities _ which, owing to the prevalence of the rifle, have become no longer tenable. It is said to be possessed of a remarkably tenacious memory, so that, according to Sir Andrew Smith, when once it has been assaulted in its watery dwelling and injured through incautiously exposing itself, it will rarely be guilty of the same indiscretion a second time, even although a very long period should elapse before its haunts are revisited. The female is less in size than the male, and is exceedingly shy, taking to the water with her young, which she usually carries astride on her neck, on the slightest alarm. It is only after long practice that the young become able to remain as long under the water as their parents, and for this reason the females while tending them come much oftener to the surface than their own necessities require. The period of gestation, as observed in females confined in the Zoological Gardens of London and Paris, extends to nearly eight months ; the young-reach maturity in five years; and thé full term of life in the species is believed to extend to thirty years. The male hippopotamus which recently (1878) died in the Zoological Gardens, London, was captured in August 1849 when only a few days old; it had thus nearly attained the age of twenty-nine, while an examination of its dead body disclosed, says Professor Owen, " no special morbid appearance to suggest that death from old age had been anticipated" (Annals and Magazine of Nat.. Hist., September 1879). The flesh of the hippopotamus is generally considered a delicacy both by natives and colonists, although according to Livingstone there are certain tribes on the Zambesi who have as great an abhorrence of hippopotamus meat as Mahometans have of swine's flesh. The fatty matter lying between the skin and the muscles is one of the purest of animal fats, and was formerly in great request among the Cape colonists when as yet those amphibians abounded in the rivers of that colony. The skin of the hippopotamus is turned to profitable account in the manufacture of elastic whips, which are in great demand throughout the African continent. The skin, according to Schweinfurth, when fresh is cut into long quadrilateral stripes, which when half-dried are trimmed with a knife and afterwards hammered out, like iron on an anvil, into round whips. As several hundreds can be made from a single hide, that part is of considerable commercial value. Still more valu-able are the tusks and incisor teeth, which, from their extreme hardness and the fact that they do not readily become yellow, have been largely used in the manufacture of artificial teeth. The hippopotamus formerly abounded in such rivers as the Nile, the Niger, the Senegal, and most of the rivers of South Africa. It is now, however, becom-ing gradually more restricted in its distribution, having disappeared altogether from the Egyptian Nile,although still abundant in its Abyssinian tributaries,as well as from the rivers of Cape colony.
The Liberian hippopotamus (Chceropsis liberiensis), the only other existing member of the family, is exceedingly rare, having been only known until recently from the two skulls on which the genus and species were founded. It differs from the common species in possessing only one pair of incisors in each jaw instead of two, and in several other minor points. A few years ago a young specimen of this rare species was brought alive to England from the Scarcies river, north of Sierra Leone, but it died soon after landing. The species is found on the west coast of Africa and on certain of the rivers flowing into Lake Chad.
Although there are thus only two living species, both of which are confined to Africa, the hippopotamus family was both larger and more widely distributed in former periods of the earth's history, fossil remains of at least nine species having been found in the Tertiary deposits of Europe and India. In Europe they occur as far north as Belgium and the south of England, but they are found nowhere in such abundance as in the island of Sicily, from which they were formerly exported in shiploads to England and France, where they were used in the manufacture of lamp-black and manure. The occurrence of these animals in a place which they could not possibly have reached had it always been an island, is regarded as one of the many proofs that dry land existed during some portion at least of the Tertiary period between Italy and Africa. (J. GI.)