Large males set up territories along riverbanks, which they defend against other males. Although neighbouring territory-holders are usually peaceful, confrontations sometimes occur. When this happens, the males challenge each other with displays, including lunging, splashing, scattering dung with their short tails and displaying their tusks with great yawns of their mouths. If neither male backs off, fighting occurs, and sometimes they attack each other with their tusks - which can lead to fatal injuries.
Males are usually aggressive towards any intruders into their territories, including young hippos. Females are aggressive when they have young, and many consider hippos to be among the most dangerous of African mammals.