Mandrill

The mandrill, Mandrillus sphinx, is the largest monkey in the world and one of the most colourful mammals. It lives in the tropical rainforests of west central Africa and sometimes crosses savannas. Its face and rear carry red and blue skin: a red stripe runs down the middle of the face to a red nose, with ridged blue skin on both sides. Its coat is olive-brown with a yellow-orange beard.

Males are far bigger than females, the most extreme size difference of any primate. Males are 70 to 95 centimetres long and weigh 19 to 30 kilograms, with canine teeth up to 4.5 centimetres, while females weigh 10 to 15 kilograms. Its closest relative is the drill. Both were once thought to be baboons, but they are closer to white-eyelid mangabeys. The IUCN lists the mandrill as Vulnerable.

Hordes of hundreds

Mandrills live in huge groups called hordes. At Lope National Park in Gabon the average horde had about 620 animals and some had 845, perhaps the largest cohesive groups of wild primates. One horde of 625 held 21 dominant males, 247 adult and young females, 200 juveniles and 86 infants.

Females and their relatives form the core of a horde, and strong family links help in fights and improve the survival of their young. Adult males mostly live alone and join the horde in the breeding season. A horde of about 700 had a home range of 182 square kilometres.

Colours and rank

A male's colours show his rank. When a male becomes the top male, his face and rear get redder, his chest glands make more scent, and his sides and rump get fatter. If he loses his rank, these changes partly reverse. Dominant males have the most contrast between red and blue and father the most young.

Males mostly settle rank with sounds and faces rather than fights. Mating is mostly in the dry season. Their preferred foods are fruit and seeds, but mandrills also eat leaves, mushrooms and animals from insects to young bay duikers.

Name and threats

The name mandrill comes from man and drill, a West African word for baboon or ape, and dates to 1744. Conrad Gessner drew the animal in 1551 to 1558 and thought it was a hyena. Linnaeus gave it a scientific name in 1758.

Habitat loss and hunting for bushmeat are the main threats, and the population may have fallen by more than 30 percent over 24 years. Gabon is considered the species' stronghold. The mandrill is in CITES Appendix I, which bans commercial trade in wild-caught animals.

On the globe

The model shows a mandrill with its red-and-blue face in the rainforest of central Africa.