Hippopotamuses: Hippopotamidae

Physical characteristics: The common hippo measures up to 106 inches (270 centimeters) in length and has a shoulder height of 54 to 60 inches (137 to 152 centimeters). It weighs up to 4,000 pounds (1,800 kilograms).

Geographic range: Although this hippo is found in thirty-five sub-Saharan countries, many of those populations are small, especially in West Africa. So, there aren't as many common hippos as it might seem there would be. Zambia, Tanzania, and the Democratic Republic of the Congo have larger populations of this species.

Common hippopotamus calves stay with their mothers until the next calf is born. (© Stephen J. Krasemann/Photo Researchers, Inc. Reproduced by permission.)

Habitat: The common hippo needs water deep enough to keep its body wet or the skin will crack from overheating. For the same reason, it enjoys wallowing in mud. Hippos leave the water at night to feed, sometimes traveling as far as 20 miles (32 kilometers) in one night.

Diet: The common hippo grazes on short grasses. The grasses become known as hippo lawns because they are nipped off so close to the ground. There has been one case of cannibalism (eating one's own species) documented.

Behavior and reproduction: The hippo is a difficult species to study because it is aggressive toward humans. The male common hippo is territorial in the water, where he defends mating rights with the female hippos in his range, but he is not territorial on land.

Hippos are known for their bellowing (shouting), but we don't know what role the bellowing plays in communicating between individuals. They also have at least three distinct calls underwater.

Common hippos mate and give birth in the water. Pregnancy lasts 240 days, at the end of which the female seeks solitude in the water. We do not know how long baby hippos nurse (drink mother's milk), but calves remain with their mothers until after the birth of the next calf. Common hippos are polygamous (puh-LIH-guh-mus; have more than one mate).

Common hippopotamuses and people: This species is highly dangerous to humans, particularly fishermen who invade their territories. It raids crops and is particularly fond of rice. Humans hunt the common hippo for its meat and ivory.

Conservation status: Though not listed by the IUCN, the total number of common hippos is low, especially in West Africa, where populations are as low as fifty. In order to rule out extinction, populations need to number at least five hundred in any given region or area. ∎