Hippopotamus

Hippopotamus, common name for certain artiodactylous (even-toed, hoofed) mammals found only in Africa. Hippopotamuses (also called river horses) are heavy-bodied, short-legged, short-tailed animals, resembling large pigs more than horses. They have large heads with small eyes and small ears; their nostrils, surrounded by sparse, bristly hairs, are equipped with special flaps that close down when the animal goes under water. The eyes and ears are located on the top of the head. The mouth is huge and contains long, pointed incisor and canine teeth. The adult common hippopotamus also has tusk-like canine teeth in the lower jaw; they grow up to 70 cm (28 in) long, weigh almost 3 kg (6 lb), and are valued as ivory. The skin, which contains a layer of fat that is about 5 cm (2 in) thick, is used to make leather whips known as sjamboks. The feet are four-toed. The meat of the hippopotamus is edible, and soup is made from the hide.

The common brown or grey hippopotamus, once widely distributed south of the Sahara Desert and along the River Nile to its mouth, and now found south of latitude 17° north, is one of the largest four-footed animals. The range of the hippopotamus has shrunk owing to human intervention. The hippopotamus reaches a length of 2.9 to 5 m (9y to 16 ft) and weighs 1,000 to 4,500 kg (2,200 to 9,900 lb). Because of its short legs it stands no higher than 1.5 to 1.65 m (5 to 5y ft) at the shoulder.

The hippopotamus is semiaquatic, spending most of the day with only its eyes, ears, and nostrils above the surface of a river, and it is capable of remaining under water for as long as 25 minutes. During the day it feeds on aquatic vegetation and often swims more than 30 km (20 mi) in search of food, emerging at night to feed on land plants. It eats sugar cane and maize and sometimes enters plantations, where it does more damage by trampling the plants than it does by feeding. Hippopotamuses have occasionally been seen in mountain rivers at heights of more than 1,500 m (5,000 ft) above sea level and at temperatures near freezing.

Common hippopotamuses travel in herds of about 10 to 15 animals, but groups of 150 individuals have been observed. The cow bears one young at a time and fights ferociously if the calf is threatened. Old bulls, like old elephants, sometimes attack other hippopotamuses or humans. The species is widely hunted, traditionally by harpooning or by digging pitfalls.

The pygmy hippopotamus is 1.5 to 1.75 m (5 to 5’ ft) long, 0.75 to 1 m (2y to 3€ ft) high at the shoulder, and weighs 160 to 270 kg (350 to 600 lb). It is found only in western Africa, especially in Liberia. It is black on top, with a greenish sheen; below, it is yellowish-green. It is less aquatic than the common hippopotamus and is found in cool forests and in marshlands. Habitat destruction and the encroachment of human populations threatens the dwindling populations of pygmy hippopotamuses.

Remains of many fossil hippopotamuses have been found in European and Indian deposits of the Pliocene epoch (5.2 million to 1.64 million years ago) and Quaternary sub-era (1.64 million years ago to the present); fossils in England, found as far north as Yorkshire, seem to be of the same species as the present-day common hippopotamus.

Scientific classification: Hippopotamuses make up the family Hippopotamidae. The common brown or grey hippopotamus is classified as Hippopotamus amphibius, and the pygmy hippopotamus as Choeropsis liberiensis.