The mandrill (Mandrillus sphinx) is a primate of the Old World monkey (Cercopithecidae) family. It is one of two species assigned to the genus Mandrillus, along with the drill. Both the mandrill and the drill were once classified as baboons in the genus Papio, but they now have their own genus, Mandrillus.
Although they look superficially like baboons, they are more closely related to Cercocebus mangabeys. Mandrills are found in southern Cameroon, Gabon,
Equatorial Guinea, and Congo. Mandrills mostly live in tropical rainforests. They live in very large groups. Mandrills have an omnivorous diet consisting mostly of fruits and insects. Their mating season peaks in July to September, with a corresponding birth peak in December to April.
Mandrills are the world's largest monkeys. The mandrill is classified as vulnerable by IUCN.
Mandrills are noted as being exceptionally colorful by mammalian standards. Charles Darwin wrote in The Descent of Man: "no other member in the whole class of mammals is colored in so extraordinary a manner as the adult male mandrill's".
The bright colors of mandrills are indeed not produced conventionally (no mammal is known to have red and blue pigments), being derived from light diffraction in facial collagen fibers.
Mandrills seem to live in very large, stable groups named 'hordes'. A horde can number in the hundreds of mandrills, possibly averaging around 615 individuals and reaching as many as 845.
It is difficult to accurately estimate horde size in the forest, but filming a horde crossing a gap between two forest patches or crossing a road is a reliable way of estimating the total number. The largest horde verifiably observed in this way contained over 1,300 individuals, in Lopé National Park, Gabon—the largest aggregation of nonhuman primates ever recorded.
The mandrill is considered vulnerable and is affected by deforestation. However, hunting for bushmeat is the more direct threat. Mandrills are particularly threatened in the Republic of the Congo. Nevertheless, there have been captive-bred individuals that have been successfully reintroduced into the wild.
According to en.wikipedia