Hippos are strict vegetarians.
The long canine teeth of a Hippo are used primarily for self defense and for fighting with each other. Although hippos are not rodents, their canine teeth, as well as their incissors, are continuously growing throughout their lives. They break off in fights and wear down naturally. The fronts of the upper canines rub on the backs of the lower canines each time the Hippo opens or closes its mouth. This grinding action helps keep their teeth from growing too long and also works as a self sharpening mechanism.