The hippopotamus or hippo, from the ancient Greek for "river horse” (sorry river pig seems a better name) is a large, mostly herbivorous mammal.  

After the elephant and rhinoceros, the hippo is the third largest type of land mamal. Despite their physical resemblance to pigs, their closest living relatives are cetaceans; whales, porpoises, etc. from which they diverged about 55 million years ago.  The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day, they remain cool by staying in the water or mud; reproduction and childbirth both occur in water.

They emerge at dusk to graze on grass. While hippo rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land. Hippos are recognizable by their barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest type of land mammal by weight (between 3,000 and 6,000 lbs.

The only heavier species on average are the white rhino, typically 3,000 lb to 7,000 lb, and the elephants, typically weighing 6,000 to 18,000 lbs. The hippo is one of the largest quadrupeds and, despite its stocky shape and short legs; it can easily outrun a human. Hippos have been clocked at 19 mph over short distances.

The hippo is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. A woman tourist was reported killed by a hippo  near Crocodile Bridge while was there. They are still threatened by habitat loss and poaching for their meat and ivory canine teeth.