Hippopotamuses

Hippopotamus Facts

Classification:

• Kingdom: Animalia
• Phylum: Chordata
• Subphylum: Vertabrata
• Class: Mammalia
• Order: Ariodactyla
• Suborder: Suiformes
• Family: Hippopotamidae
• Genus and species:Hippopotamus amphibius (hippopotamus),Choeropsis liberiensis (pygmy hippopotamus)
• Geographical location: Although once numerous in the rivers throughout Africa,H. amphibius can now be found only south of Khartoum and north of the Zambezi River; the pygmy hippopotamus is found in West African lowland rain forests
• Habitat: Hippopotamuses live in short grasslands, rivers, and lakes; pygmy hippopotamuses live in lowland forests and swamps
• Gestational period: Eight months for hippopotamuses, seven months for pygmy hippopotamuses
• Life span: Up to forty-two years in the wild, past fifty in captivity
• Special anatomy: The genera differ greatly in size, but both have a broad snout, a very large mouth, a short round body, and short stocky legs; the smooth, hairless skin is covered with special pores that secrete a pinkish substance known as blood sweat, which is protective when in the water or dry land; large canine teeth enlarge into tusks that grow continually; the stomach is three-chambered but is non ruminating; hippopotamuses appear to have good eyesight, hearing, and smell

The name hippopotamus means “river horse,” and these mammals spend most of their time in the water. They have inflated-looking bodies that resemble barrels, supported on short, pillar-like legs with four toes ending in hooflike nails. The tail is short and bristled, with flattened sides. The belly is carried only a few inches above the ground. The eyes are raised on top of a flat head, the ears are small, and the nostrils are slits high up on the muzzle and can be closed when the animal is submerged. The two species, H. amphibius and C. liberiensis (pygmy hippopotamus) differ greatly in size, with the former up to 5.5 feet high and weighing seven thousand to ten thousand pounds. The pygmy hippopotamus is much smaller, with an average height of 2.5 to 3 feet, and weighing 350 to 600 pounds.

Hippopotamus Life

Hippopotamuses must submerge frequently because their naked skin is vulnerable to overheating and dehydration. They can stay submerged up to thirty minutes. Their skin has a brown to gray-purple coloration with pinkish creases. The pygmy hippopotamus is black-brown to purple in color with the cheeks often tinted pink. Unlike the pygmy hippopotamus, which is a solitary mammal dwelling in rivers and forests, H. amphibius is a huge animal that can be found in herds of up to eighty members.

Seeking food, H. amphibius travels at night from the rivers for grazing, but will return before dawn to spend the day digesting and socializing in the riverbeds. During the forays from the water, the animals typically travel two to three miles. H. amphibius eats up to ninety pounds of grass on a nightly basis, often mowing twenty-inch-wide swaths with its muscular lips and mouth. The pygmy hippopotamus prefers to seek food on high, dry ground and is most active between 6:00 p.m. and midnight. They have home ranges that may cover between one hundred and four hundred acres. Most movements are along established paths in their home range, and rarely do they cross paths with others of their own species. During these forays, they seek water plants, grasses, fallen fruits, and leaves.

For H. amphibius, their watery homelands are partitioned into individual mating territories by mature bulls that defend defined sections. These territories can remain fixed for years. Dung showering is used to mark territories and express dominance. Other behaviors that signal threats can include water scooping, head shaking, grunting, roaring, explosive exhaling, and charging. Submission is signaled by turning tail, approaching in a crouched position, lying prone on the land, or diving and swimming away from the dominant male.

Reproduction

Herds usually breed between ten to fifteen hippopotamuses. Non breeding males are tolerated in the territories if they do not bother the cows. Cows and calves associate in nursery herds and establish calf crèches, which serve as protection against predation from crocodiles, lions, and hyenas. Mating takes place during the dry season while the animals are in the water. After the birth of a calf, either on land or in the water, the cow remains with the calf for about a month before returning to the herd. Baby hippopotamuses are able to nurse underwater until they are weaned, at around eight months of age.

During mating season, the solitary pygmy hippopotamus seeks out a receptive female who tolerates the male’s presence when in heat. One to four copulations may take place over a period of two days on both land and in the water. The young are born on land or in the water and remain concealed for three to four weeks. The main predator for the pygmy hippopotamus is the leopard. The pygmy hippopotamuses are considered to be in jeopardy for survival because of hunting and destruction of habitat by logging, and as of 2016 they were listed as endangered by the International Union for Conservation of Nature. The common hippopotamus, on the other hand, had been listed as vulnerable in 2008.

Principal Terms

blood sweat: oily secretion from mucous glands serving a protective function

calf crèche: group of newborn calves in a place of protection

dung showering: behavior by bulls to show dominance over other males

nonruminating: digesting grasses without chewing cud

Bibliography

Alden, P. National Audubon Society Field Guide to African Wildlife. Knopf, 1995.

Brust, B. W. Zoobooks: Hippos. Wildlife Education, 1989.

Burton, M., and R. Burton. The Marshall Cavendish International Wildlife Encyclopedia. Rev. ed., Cavendish, 1990.

Eltringham, S. Keith. The Hippos: Natural History and Conservation. Academic, 1999.

Happold, D. C. The Mammals of Nigeria. Oxford UP, 1987.

"Hippopotamus." African Wildlife Foundation, n.d., www.awf.org/wildlife-conservation/hippopotamus. Accessed 3 Oct. 2016.

Kingdon, J. The Kingdon Field Guide to African Mammals. Academic, 1997.