A scientific study recently suggested that these animals that were present in West Africa no longer exist in the wild and the species went extinct in this part of the world. Actually, the expected last animals failed to be found in Northern Cameroon.
Consequently, the West African black rhino sub-species has been tentatively declared extinct.
In Africa, another black rhino and four white rhino sub-species (all grey, by the way) are also on the brink of extinction due to continuous poaching and competition between rhinoceros and man for their natural habitat.
More information about the rhinoceros: Wikipedia.