The rhinoceros is a large, primitive-looking mammal that in fact dates from the Miocene era millions of years ago. In recent decades rhinos have been relentlessly hunted to the point of near extinction. Since 1970 the world rhino population has declined by 90 percent, with five species remaining in the world today, all of which are endangered. Rhinos live in home ranges that sometimes overlap with each other. Feeding grounds, water holes and wallows may be shared. The black rhino is usually solitary. The white rhino tends to be much more gregarious. The black rhino is a browser, with a triangular-shaped upper lip ending in a mobile grasping point. It eats a large variety of vegetation, including leaves, buds and shoots of plants, bushes and trees. The white rhino, on the other hand, is a grazer feeding on grasses.