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 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 underwater. 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 common adult hippopotamus also has tusklike canine teeth in the lower jaw; they grow up to 70 cm (up to 28 in) long, weigh almost 3 kg (6 lb), and are valued as ivory. The skin contains a layer of fat that is about 5 cm (2 in) thick and 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 gray hippopotamus, once widely distributed south of the Sahara and along the 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 due to human intervention. The hippopotamus reaches a length of 2.9 to 5 m (9.5 to about 16.5 ft) and weighs 1000 to about 3600 kg (2200 to about 8000 lb). Because of its short legs it stands no higher than 1.5 to 1.65 m (5 to 5.4 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 underwater for as long as 25 minutes, though it usually does so only for 3-5 minutes at a time. During the day it feeds on aquatic vegetation and often swims more than 30 km (more than 19 mi) in search of food, emerging at night to feed on land plants. It eats sugarcane and corn 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 1500 m (5000 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 attacked. 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 (4.9 to 5.7 ft) long, 0.75 to 1 m (2.5 to 3.3 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. Pygmy hippopotamuses almost always travel in pairs or groups of three immediate family members, rarely forming a herd.

Remains of many fossil hippopotamuses have been found in European and Indian deposits of the Pliocene Epoch and Quaternary Period; fossils in England 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 gray hippopotamus is classified as Hippopotamus amphibius  and the pygmy hippopotamus as Choeropsis liberiensis.