The common patas monkey (Erythrocebus patas), also known as the wadi monkey or hussar monkey, is a ground-dwelling monkey distributed over semi-arid areas of West Africa, and into East Africa. There is some confusion surrounding if there are valid subspecies, with some listing four, others three, and others listing two: the western Erythrocebus patas patas (with a black nose) and the eastern E. patas pyrrhonotus (with a white nose). However, it was later discovered that the nose colour used to separate these subspecies could change to white during pregnancy in females, as well as in general as animals aged, and E. patas pyrrhonotus in Kenya often did not have white noses, thus Mammal Species of the World has classified E. patas as a monotypic species.