mandrill, large monkey, Mandrillus sphinx, of central W Africa, related to the baboons. Mandrills are found in forests, while baboons live in open country. The fur of the mandrill is mostly dark brown, but the bare areas—face and buttocks—are patterned in bright colors that are especially spectacular in the adult male, the most colorful of all mammals. The long, heavy doglike muzzle has bright red skin covering the chin, mouth, and nose and extending upward in a narrow strip to the striking, close-set, yellow-brown eyes. The cheeks are bright blue and are folded into an elaborate pattern of ridges. The fur around the eyes is black, and the beard and the edges of the mane are pale yellow. The buttock pads are bright blue, red, and purple. The tail is a short stump. Male mandrills, about 3 ft (90 cm) long, are considerably larger than females and have enormous canine teeth that they display in yawnlike threatening gestures. Mandrills travel on the ground in small family groups, feeding chiefly on insects and vegetation. Powerful animals, and formidable when provoked, they are retiring in habits and avoid contact with humans. They are extremely difficult to observe in the wild. The closely related drill, M. leucophaeus, is also a forest dweller. It is brown with a black face partially outlined in red; the buttock pads are pink. The mandrill and the drill are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Primates, family Cercopithecidae.

Diurnal monkey (family Cercopithecidae, usually genus Mandrillus) of equatorial African rainforests, known for its striking colouring. The stout-bodied, primarily terrestrial mandrill has a short tail, prominent brow ridges, and small, close-set, sunken eyes. The ribbed bare skin on the adult male's cheeks is bright blue, with scarlet on the nose; the buttock pads are pink to crimson, shading to bluish; and the beard and neck are yellow. The adult male is about 3 ft (90 cm) long and weighs about 45 lb (20 kg); the female is duller and smaller. Mandrills eat fruit, roots, insects, and small reptiles and amphibians.

Learn more about mandrill with a free trial on Britannica.com.