Studying the interactions of hippos is difficult because they lack sexual dimorphism - males and females are virtually indistinguishable. Although they stay close, they do not form social bonds. In the water, the dominant males defend a section of the river about 250 meters long, with about ten females per section. The largest herd consists of about 100 individuals. Copulation laws define these territories. In the herd, there is segregation by sex - they group themselves according to sex. When feeding, they do not manifest territorial instincts.
