This monkey is critically endangered and may be the monkey closest to extinction in Africa, with only 100-200 remaining in the wild, living in Kenya and Tanzania.

It was initially described as a species in 1905, but was then relisted as a sub-species of the common Patas monkey. It was once again made a separate species back in 2017. For a number of reasons, it has been suggested that it may represent an earlier Patas monkey which has been surplanted by the common Patas monkey across much of its former range.