Found in southern Cameroon, Gabon, Equatorial Guinea, and the Republic of the Congo.
They have an omnivorous diet consisting mostly of fruits and insects.

Mandrills are noted as being exceptionally colorful by mammalian standards. Charles Darwin wrote in The Descent of Man: "no other member of the whole class of mammals is coloured in so extraordinary a manner as the adult male mandrill". The bright colors of mandrills are produced by structural coloration in facial collagen fibers; no mammal has blue pigment.

Other mammals