In the Okavango Delta inhabit large number of hippos, visible during Water Safari Camp Eagle Island Camp by Orient Express, outside the Moremi Game Reserve in Botswana. The common hippopotamus (Hippopotamus amphibius) is a large mammal primarily herbivorous artiodactyls living in sub-Saharan Africa. It, along with pygmy hippopotamus (Choeropsis liberiensis), one of only two current members of the family Hippopotamidae. It is a semi-aquatic animals inhabiting rivers and lakes where territorial adult males with groups of 5-30 females and young control a river area. During the day they remain in the water or mud, and both intercourse and delivery of this animal occur in water. At dusk they become more active and out to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity, and are not territorial on land. Despite their physical resemblance to pigs and other terrestrial ungulates, their closest living relatives are cetaceans (whales, porpoises, etc..) Of which diverged about 55 million years. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The hippopotamus fossils earliest known members of the genus Kenyapotamus in Africa, date to make about 16 million years. The hippopotamus is recognizable by its barrel-shaped torso, enormous mouth and teeth, body skin smooth and nearly hairless, stubby legs and large size. Earth is the third animal by weight (between 1 ½ and 3 tonnes), behind the white rhinoceros (1 ½ to 3 ½ tonnes) and the two genera of elephants (3-9 tons). Despite its stocky shape and short legs, can run as fast as the average human. Hippos have been clocked at 30 km / h over short distances. It is one of the most aggressive creatures in the world and is often regarded as the most ferocious animal in Africa. There are approximately 125 000 150 000 hippos throughout Sub-Saharan Africa, Zambia (40,000) and Tanzania (20 000-30 000) have the largest populations. Are threatened due to habitat loss and poaching for their meat and ivory canine teeth.