Calves nurse underwater and are frequently seen riding upon their mothers' backs while the mother is in the water. Behavior The hippopotamus typically sleeps during the day and maintains activity at night. It is not, however, strictly nocturnal. Hippos may cover up to 33 km of water each night in search of food. They eat mainly the grasses along the shores of the rivers they inhabit, but they have been seen grazing up to 3.2 km from the shoreline.
Hippos are extremely graceful in the water, despite their clumsy appearance on land.
Their specific gravity allows them to sink to the bottom of rivers and literally walk or run along the bottom. Hippos may occur singly or in groups of up to 30 animals. The central core of social groups appears to be females with their dependent offspring. Adult males vie for control of these herds. Aggression between males is intense.