The deep grunting of hippo is one of Africa's characteristic sounds and most people who have been on an African safari will have heard the sound. Although they are grazers hippos are blessed with massive teeth that are used in territorial fights and displays. These teeth are also used to defend territories from humans.
Besides isolated cases of hippo where they are hunted by lions their main threat is from humans. That said there is a pride of lions in northern Botswana that used to prey on hippo regularly. The majority of hippo / predator interaction is from hippo defending their territories from roaming predators.
Hippos' reaction to predators shows an inherent dislike and on a number of occasions I have witnessed hippos chasing predators of a kill. On the Chobe floodplains one morning I watched as a pack of wild dogs pulled down a Puku near the water's edge. As they started feeding a hippo charged out the water and chased them off. This continued for some time until the wild dogs gave up and moved off.
Aside from their tendencies to chase predators off hippo have been observed to catch and kill antelope that have strayed into the water. Why this happens is unknown but has happened enough times to be considered a form of behaviour and not an aberration.
Hippos are known to wander great distances at night in search of food. In Botswana I observed a hippo that had wandered too far from the Linyanti system one night and ended up in the Savuti Marsh area. Its time of arrival in Savuti coincided with a water crisis.
The waterholes were dry and many animals were milling around in confusion. The hippo was stranded at one of the dry pans. The days were scorching, adding to the problem. The most fascinating part of this drama was the other animals' reaction to the hippo.
hyenas lay side by side with the hippo in one of the concrete troughs in an apparent move to cool down on the concrete. Elephant would walk over, have a look then walk back to the little shade there was.
When the water finally came through the pipe on the third day the elephants kept other animals away from the trough with the hippo, even chasing the hyenas away that were sharing the trough at the time. It was an amazing behavioral trait.The hippo recovered and disappeared during the third night.