Hippo's skin is very thin and devoid of sweat glands, which means hippos can rapidly dehydrate and overheat. So most of their day is spent under water with only eyes, ears and nostrils showing. Hippos can stay submerged for up to five minutes. A hippo by day is a vocal, densely social and sedentary wallower. By night it is a silent, solitary grazer on land and very dangerous for the people. The hippos are responsible for the most people killings under all animals in Africa.
A hippo can ingest up to 60 kg in a night's grazing and seldom needs more than 5 hours out of water. Large populations of hippos alter grass composition and inhibit fires by removing potential fuel. It is possible that such populations cause long-term vegtation cycles because their progressive degradation of the grazing increasingly encourages regeneration of thickets.
The hippos have a big impact on the life in the water through their great accumulations of dung. Many small animals and fishes feed on the hippo's dung. Are the hippos exterminated, impoverishes the biological live in the lakes and rivers.
