Other primates are Preuss's Monkey, Red-eared Guenon, Greater Spot-nosed Monkey and several species of Bush baby, Collared Mangabey, Chimpanzee and Preuss's Red Colobus.

Both were formerly considered subspecies of a widespread Cercocebus torquatus.

The collared mangabey (Cercocebus torquatus), also known as the red-capped mangabey, or the white-collared mangabey (leading to easy confusion with Cercocebus atys lunulatus), is a species of primate in the Cercopithecidae family of Old World monkeys.

Scientists believe two monkey viruses were involved because the virus from guenons (Cercopithecus nictitans) was closest in the part of the genome that contains the code for the virus's protein envelope, while the virus from the mangabey (Cercocebus torquatus) was closest in a different segment.