Hippos are recognizable by their barrel-shaped torsos, enormous mouths and teeth, nearly hairless bodies stubby legs and tremendous size. They are the third-largest type of land mammal by weight the only heavier species on average are the white and Indian rhinoceroses typically 1½ to 3½ tonnes and the elephants, typically weighing 3 to 9 tonnes. The hippopotamus is one of the largest quadrupeds and, despite its stocky shape and short legs it can easily outrun a human. Hippos have been clocked at 30 kmover short distances. The hippopotamus is one of the most aggressive creatures in the world and, as such ranks among the most dangerous animals in Africa. Nevertheless, they are still threatened by habitat loss and poaching for their meat and ivory canine teeth.
The hippopotamus is semiaquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of five to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grasses. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land.