Mandrill Mandrillus sphinx

Head and body length is 610-764 mm and tail length is 52-76 mm. Weights of males are average 25 kg and 11.5 kg. for females. This species is the largest of all monkeys measuring 508 mm at the shoulder and weighing as much as 54 kg. The facial features are distinguished be an outgrowth of six ridged and grooved bone which are seen as prominent ridges along the length of the nasal bones. In adult males the skin in the grooves is purple and blue on the ridges. The area between each set of ridges is a bright scarlet extending forward to the muzzle and around the nostrils. Females have less pronounced ridges, lacking the purple coloration in the grooves and the scarlet is replaced by black. The buttock pads of both males and females are furless and have a lilac tinge with reddish purple edges. This coloration may facilitate group movement through thick vegetation. The brightly colored skin of M. sphinx becomes intensified when the animal becomes excited. The fur on the top of the head is a tawny green and the underparts are yellowish.

Preferred habitat is dense rainforest where the heavier males travel along the ground and the smaller females and babies are found mid-level in the trees. After foraging on the ground for fruits, plant material, mushrooms, invertebrates, and sometimes small vertebrates, they enter sleeping trees in the late afternoon.

Home ranges are relatively large, spanning 40-50 sq km. Social groups are comprised of 1 adult males, 5-10 adult females and an average of 10 juveniles. These smaller groups some together in the dry season, resulting in troops of as many as 200 individuals. Adult males without harems are solitary. Reproduction appears to be seasonal with most births occurring between the months of January and April in the population studied in Gabon. Gestation is 168-176 days.

M. sphinx is found south of the Sanaga River in Cameroon; Rio Muni (Equatorial Guinea); Gabon; and Republic of Congo.