Of all the rhinoceros species, black rhinos are most closely related to white rhinos (Ceratotherium simum), but there are a number of respects in which the two species differ. Black rhinos are smaller than white rhinos. Black rhinoceroses also have a smaller head which they hold higher and in horizontal orientation. White rhinos have a comparitively larger head which they hold lower to the ground. The lips of black rhinoceroses are also unique. They have a pointed upper lip that is muscular and enables them to grasp shrubs and vegetation which they pull from the ground as they eat.
Black rhinos were once the most numerous of the five rhino species. Sadly, their population has plummeted by more than 90 percent since the 1940s. In 1995, the rhino population fell to just 2,410 individuals. Since that time their numbers have recovered modestly but the species remains classified as Critically Endangered on the 2008 IUCN Red List of Threatened Species.
The main threats to black rhinos are poaching and habitat destruction. The horns of the black rhinoceros are prized for use in traditional medicine and for carvings and ornaments. As a result, intense poaching of black rhinos has been a major force in the decline of the black rhino population. Additionally, conservation efforts have been marred by civil unrest in regions such as Angola, Cameroon, Central African Republic, Chad, DR Congo, Mozambique, Namibia, Rwanda, Somalia, Sudan and Uganda.
Black rhinos have a poor sense of sight but acute sense of smell. When threatened, black rhinos may charge, although in some cases the charges are bluffs and the animal stops a few feet before it makes contact with its target. Black rhinos inhabit home ranges, and individual territories often overlap. Waterholes are necessary parts of a rhino's home range, as it provide water for drinking as well as wallowing.