The hippopotamus can weigh up to five thousand and seven hundred pounds. The eyes, ears, and nostrils are positioned to stick out of the water when the rest of the hippo is submerged. Hippos spend the daytime wallowing in water. At night they come out on land to graze on grasses and other vegetation. They can eat up to one hundred and thirty pounds per night. Hippos live in schools of fifteen to thirty animals, bulls, cows, and calves. Schools are about equally divided between males and females. Males often fight for dominance and many bare the scars of these battles. Hippos can be very dangerous to humans, particularly if they find you on land blocking their escape route to water. Although they have stubby legs they can run as fast as humans. In the ancient Greek language hippopotamus meant "river horse".