The common hippopotamus constitute a family by themselves. They are bulky animals, with large heads that seem too large and heavy for its owner, since the animal may frequently been seen resting its ungainly muzzle on the ground, as though to relieve the neck from the strain of its weight. The common hippopotamus is by far the larger of the two living species, and next to the elephant would seem to be the bulkiest of all existing terrestrial Mammals.
This species is further characterized by having two pairs of incisor teeth in each jaw, the middle lower pair being of far larger dimensions than the others. The general color of the skin is a slaty copper-brown, tending more to blackish brown on the back and purplish brown beneath. There is, however, considerable sexual and individual variation in this respect; and the hue of the skin also varies according to whether the animal has recently emerged from the water, or whether it is thoroughly dry. While the males are of a dark color, the females are of a yellowish brown; and when the hippopotami first leave the water the upper-parts appear brownish blue and the under-parts almost flesh-colored, but when thoroughly dry the color of the back is blackish brown or slaty.
That the hippopotamus formerly inhabited Lower Egypt is indicated by the occurence of its remains in the mud of the delta, while this is also confirmed by the frequency with which it is depicted in the ancient frescoes of that country. one of these temples preserved in the temple of Edfu shows that the ancient Egyptians were in the habit of harpooning these animals. in East, South, and West Africa the hippopotamus comes much nearer to the coast than in the north, and in many districts it is to be found quite close to, or even in the sea itself.
The hippopotamus is more essentially an aquatic animal, the greater portion of its time being spent in the water, where movements are far more rapid and natural than they are on land. As the carcass of a hippopotamus when freshly killed sinks rapidly to the bottom, the specific gravity of the animal when the lungs are inflated with air cannot be far, if at all, below that of water, and the animal is consequently enabled to stay without difficulty at the bottom of a river or lake, where it can run with ease and speed. When undisturbed, the average duration of time during which the hippopotamus remains under water does not exceed five minutes; but in regions where these animals are much hunted the length of the immersion is often greater, sometimes extending to as much as ten minutes. When a hippopotamus comes to the surface it generally sprouts up a column of water by the violent blowing-out of air through the nostrils, accompanied by a loud snorting noise. A peculiarity about the hippopotamus is that when swimming in the water and about to dive, it gradually subsides by slowly sinking the hind-quarters and afterwards the rest of the body, instead of sinking down head-foremost. When on a high bank and suddenly frigtened, it will not, however, hesitate to precipitate itself headlong into the water.
As the giraffe may be regarded as the most characteristic and striking animal on an African desert-landscape, so the hippopotamus forms the most distinctive living feature in a river-scene; and nothing can be more impressive than to come suddenly upon a herd of these gigantic animals on the margin of some unfrequented river or lake. During dry season a bend o f river can become so crowded with hippopotomi. The banks of rivers are marked by numerous furrows made by these animals in ascending during the night to graze on the herbage of the adjacent lands, and they are guided back to these paths solely by scent, if heavy rain comes on during their nocturnal excursions they are unable to find their way back to the river, and stand helpless on the land. The males generally remain in company with the females, although a very few aged individuals of the former sex may lead more solitary lives. The still reaches are their favorite haunts, as elsewhere the constant exertion necessary to keep themselves form being carried down the stream disturbs their nap. They remain by day in a drowsy state, taking little notice of things at a distance. The males utter loud, snorting grunts, which may be head a mile off. The young ones stand on the necks of their dams, and their small heads appear above the surface as they rise to breathe. The dam, knowing the more urgent need of her calf, rises more frequently when it is her care.
The hippopotamus is a purely herbivorous animal, and form its gigantic bulk consumes an enormous amount of food. The capacious stomach, which, when extended, measures some 11 feet in length, is indeed capable of containing between five and six bushels, which gives some idea of the vast quantity of nutriment the creature requires. In uncultivated districts, grass and various water-plants- more especially the lotus and papyrus- afford the chief food-supply ; but where the land adjoining the rivers is under cultivation, the damage done to growing crops of rice, millet, maize, and sugar by hippotomi is incalculable. It is not only the amount they eat (although this is large enough), but the quantity damaged in their passage from one part of a field to another. Water-plants are dragged up by the roots from the beds of rivers and lakes, when not too deep, by the hippopotamus in its capacious mouth, and after being brought to the surface, are devoured at leisure. When starting for their nocturnal excursions in the field, these animals seldom leave the river till about an hour after sunset, and do not return until dawn. On such expeditions they make a prodigious snorting and grunting, which may be heard for long distances.
