Although they are herbivores, hippopotamuses are considered as Africa wildest animals because of their aggressive nature. When they are out of the water, hippos are able to run up to 50 km per hour. They have an influence on the course of rivers and swamps by using the very same walking paths day after day and thus diverting the water into these furrows. Hippos spend daytime in the water and graze in the evening. Within only five hours, a hippo is able to devour more than 70 kg of food, In the water, the males are very keen on defending their territory - however, there is no rivalry once they are ashore. Although they cannot swim, hippos fight, sleep and mate in the water. They live in pods of approximately thirty individuals. With a length of more than five metres and weighing up to two tons, hippos rank among the largest land mammals. They can grow quite old - often up to forty years.