What's in a name?Watch a hippo, on land or in the water, and you’ll soon discover that this roly-poly is one of theworld’s great characters. It is the most rotund land mammal and spends its daytime hours in lakes, pools, mudholes, or in the preferred moving waters of rivers.
The name “hippopotamus” comes from a Greek word meaning “water horse” or “river horse.” But hippos are not related to horses at all—in fact, their closest living relatives may be pigs or whales and dolphins! There are twospeciesof hippopotamus: the river, or common, hippo and the much smaller pygmy hippo.
Hippos have unique skin that needs to be kept wet for a good part of the day. Staying out of the water for too long can lead to dehydration, so hippos try to remain in water during the day. They don’t have true sweat glands; instead, hippos secrete a thick, red substance from their pores known as "blood sweat," as it looks like theyaresweating blood. But not to worry! The blood sweat creates a layer of mucous that protects hippo skin from sunburn and keeps it moist. It is thought that this mucous may also prevent infections; even large wounds don't seem to get infected despite the filthy water hippos sometimes live in in their native habitat.
In the unpredictable African wilderness, hippos face many perils, such as disease anddrought. A full-grown adult doesn’t have much in the way of natural predators. Lions have been known to take down hippos, but it depends upon how many lions, the age of the hippo, and how far it is from the water.
But simply reaching adulthood is a challenge. Crocodiles, lions, hyenas, and leopards are all potential threats while growing up—but the most dangerous thing to a young hippo is another hippo. When you live in a group that may contain as many as 100 individuals, disagreements are bound to happen. Sometimes young hippos get caught in the middle of violent clashes between adults and can be bitten or crushed—occasionally by their own parent.
Despite the hippos' cute appearance, they are among the most dangerous and aggressive of all mammals. Theircanineand incisor teeth grow continuously, with canines reaching 20 inches (51 centimeters) in length. Hippo males especially use their canines for fighting. To ward off enemies, a hippo may yawn, scoop water with its mouth, shake its head, rear up, lunge, roar, grunt, chase, and make a loud wheezing sound, all of which are threat displays. A hippo can kill people if it's provoked or feels threatened. But the impressivetusksandcanine teethare used mainly for defense or fighting with other hippos.
