The hippopotamus (Hippopotamus amphibius) is a large, mostly plant-eating African mammal, one of only two extant species in the family Hippopotamidae (the other being the Pygmy Hippopotamus).
The hippopotamus is a semi-aquatic mammal, inhabiting rivers and lakes in sub-Saharan Africa in large groups of up to 40 hippos. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water, where territorial bulls preside over a stretch of river. While hippos rest near each other in territories in the water, grazing is a solitary activity and hippos are not territorial on land.
Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans—whales, porpoises and the like. The common ancestor of whales and hippos split from other even-toed ungulates around 60 mya. The earliest known hippopotamus fossils, belonging to the Kenyapotamus in Africa, date to around 16 mya.
Although there are an estimated 125,000 to 150,000 hippos throughout Sub-Saharan Africa, they are still threatened by poaching and habitat loss. (Read more...)