Hippo fights can last several hours, or even days. Hippos are aggressive and, although both genders fight, males battle each other more regularly and more seriously, usually over territory or females. However, many conflicts are short lived. Disputes between adult males begin with a yawning, dominance display that shows off their formidable teeth. The contestants then scoop water at one another. Unless one of them submits by lowering his head, a full-scale fight follows. During the fierce battle the sharp canine tusks are used to stab and slash the opponent's head and shoulders, sometimes inflicting fatal wounds.