This black rhinoceros was on a private game reserve (over 100 square miles, fenced in) outside of Nairobi.  The upper lip is the easiest way to distinguish the two species.  The black rhino has a pointed, somewhat prehensile lip.   The white rhino has a wide, flat lip and a head that seems too large for its body.   One of the females that we saw had fresh wounds on her flanks.  Presumbaly they were inflicted by an over-zealous suitor.  There are no lions within the preserve.  It was not mentioned, but I assumed that the owner got income from both tourism and big game hunting.  Most African species are at least partially migratory.   In a restricted and confined habitat, the number of grazers would have to be controlled somehow so that they did not degrade their environment through over-grazing.   Predators, human or otherwise, are a vital part of the balance of nature.