Hippopotamus normally occur in herds or schools of ten to fifteen individuals. Schools are usually composed of cows and young
of various ages with a dominant bull in overall control. Territoriality is strongest close to the water.
Standoffs occur between two territory holders at the boundary and are most often peaceful. First the two stare, mark the area
with faeces and urine, and flap their tails to spread their dung. Usually the two bulls go their separate ways after this early
stage. If not, ritualized fighting follows. During this stage, the males face each other and splash water with open mouths without
any physical contact. One will jut forward and the other will retreat. On some occasions, however, the dominant males will engage in
intense fighting. The fights include long chases in the water and on land and result in deep gashes.