According to recent studies, approximately one in four mammals and one in eight birds currently faces a high risk of extinction. Though species extinction is natural, the current rate of extinction is at least 1,000 times faster than the natural rate. The leading cause of extinction around the world is habitat loss. Extinction rates are growing the fastest in areas with high population growth. In Kenya, armed men are currently standing on guard 24/7 as the last known northern white male rhino wanders around a conservation area. Even with human intervention, it is unlikely that the last male of the subspecies will be able to reproduce with either of the two last females in his habitat.