Mandrill

Name and taxonomy

The word mandrill joins man to drill, a West African word for a baboon or ape, and dates from 1744. It seems to have referred first to chimpanzees. Buffon was the first scholar to attach it to this monkey, in 1766. Thomas Pennant called it the tufted ape, the great baboon and the ribbernosed baboon in the 1770s and 1780s. Conrad Gessner pictured it in the 1550s and took it for a kind of hyena.

Linnaeus named it Simia sphinx in 1758, and Ferdinand Ritgen created the genus Mandrillus in 1824. For much of the twentieth century it sat in the baboon genus Papio. Genetic work then showed a closer tie to the white-eyelid mangabeys, Cercocebus. Two studies in 2011 settled Mandrillus and Cercocebus as sister lineages. Authors have proposed northern and southern subspecies, but the consensus is a single one, M. s. sphinx. A third subspecies from Bioko Island rested on a mistake: no mandrills live there.

Evolution and relatives

The mandrill's only congener is the drill, Mandrillus leucophaeus, which has a black face. The two split about 3.17 million years ago. Their line parted from the mangabeys about 4.5 million years ago. No fossil of the genus has ever been found. The Sanaga River keeps the mandrill and the drill apart today.

Within the species, the animals on each side of the Ogooué River separated about 800,000 years ago. They carry different lineages of the simian immunodeficiency virus, which split with them. A draft genome appeared in 2020 at 2.90 billion base pairs. The baboon-like face and body are thought to be convergent, shaped by the same life on the ground.

Appearance

The mandrill is stocky, with a big head, a long muzzle and a stubby tail held upright. Males reach 70 to 95 centimetres in head and body, and females 55 to 70 cm. Males weigh 19 to 30 kilograms and females 10 to 15 kg. ADW records a male of 54 kg and gives a standing height of about 80 cm. The tail is only 7 to 10 cm long. A male's canine teeth reach 4.5 cm, a female's about 1 cm.

The coat is grizzled olive brown, paler below, with a yellow-orange beard and white whiskers round the lips. A male wears a crest of long hair on the head and neck. A red stripe runs down the centre of the face into the red nose. On each side the skin is blue and grooved, and in males bony swellings hold up the ridges. A male's rump and genitals show red, pink, blue and purple, with a violet scrotum. Females are duller, and some have faces that are almost black.

The red comes from blood vessels close to the surface. The blue is structural: parallel collagen fibres scatter light, as in no pigment. The blue ridges stand out against both the red face and the green of the forest. Cheek pouches let the animal carry food away to eat later.

Habitat and range

The mandrill lives in west-central Africa, in southern Cameroon, mainland Equatorial Guinea, Gabon and part of Congo. The range ends at the Sanaga River in the north and at the Ogooué and Ivindo rivers in the east. Gabon holds the stronghold of the species. GBIF lists occurrence records from 23 countries, most of them zoo and museum specimens far outside this range.

It prefers primary rainforest but uses secondary forest, gallery forest in savanna and mountain forest. It crosses grassland between forest patches and visits farm fields. It likes thick bush of gingers and other perennial plants. It spends the day on the ground but feeds up to the canopy and sleeps in trees, choosing a new tree most nights. Talapoins, guenons, mangabeys, colobus monkeys, chimpanzees and gorillas share its forest.

Diet and feeding

The mandrill is an omnivore that eats more than a hundred plant species. At Lopé National Park the diet was 50.7% fruit, 26.0% seeds, 8.2% leaves, 6.8% pith, 2.7% flowers and 4.1% animal matter. It eats more seeds than most primates, and adult males can crack the hard shells of Detarium seeds. Favourite fruits include the cashew relative Pseudospondias and the coffee relative Nauclea. It also takes young shoots and the pith of gingers and arrowroots, and mushrooms.

Animal food is mostly ants, termites, crickets, spiders, snails and scorpions. It eats birds and their eggs, frogs and rodents. Mandrills have killed young bay duikers with a bite to the head, then torn off the hind legs and opened the belly. Animals sometimes hunt together and share the kill. In the wet season hordes forage in continuous forest, where fruit is rich, and in the dry season along gallery forest and savanna edges. Males forage mainly on the ground, while females and young search the middle levels of the trees.

Behaviour and social life

Mandrills are diurnal and active for about 10 hours a day. They live in hordes that can hold hundreds of animals and stay together rather than splitting and merging. At Lopé, hordes averaged 620 animals and one reached 845. One horde of 625 held 21 dominant males, 71 lesser males, 247 females, 200 juveniles and 86 infants. A horde of about 700 used a home range of 182 square kilometres. A group of 120 used 8.6 km2 and walked 2.42 km a day.

Females and their relatives form the core of the horde. Dominant females sit at the centre of the social network, and a mother's rank shapes the rank of her sons and daughters. Adult males are not permanent members. They join when females come into season and leave when the season ends, and no bachelor groups are known. High-ranking males stay near the centre of the horde, low-ranking ones at the edge, and female coalitions can drive a male out.

Both sexes rub their chest glands on trees, and dominant males mark most of all. The scent tells others the marker's sex, age and rank. Mandrills groom each other freely, and a subordinate grooms from behind to keep an escape route open. Captive mandrills use sticks to clean themselves, and a group at Colchester Zoo invented a face-covering gesture that asks not to be disturbed.

Communication and senses

The face is the mandrill's main signal. A threat is an open-mouthed stare, with the head bobbing, the hair raised and a hand slapping the ground. A subordinate answers with a bared-teeth grimace. Young and low-ranking females pout in a duck face to show anxiety. A relaxed open mouth invites play, and a male approaching a female grins and smacks his lips. Head and shoulder shaking invites grooming.

Adult males give two-phase grunts and roars during group moves, the equal of a baboon's wahoo bark. Other animals give crowing calls that last almost two seconds. A sharp repeated yak marks tension, a growl mild alarm, and a two-syllable k-alarm real danger. Screams signal fear, and a purring girney soothes or complains among females and young. Related animals sound alike, and unrelated animals that spend time together come to sound alike too. Males read a female's fertility by scent with the vomeronasal organ, using the flehmen grimace.

Reproduction and life cycle

The dominant male sires most of the young. When a male reaches the top, his testes grow, his face and rump redden, his chest gland runs and his flanks fatten. Biologists call such animals fatted males, and the changes reverse if he falls. Males with canines under 30 millimetres rarely father offspring. Rank is mostly settled by calls and faces, not fights.

Mating peaks in the dry season, with ovulation between June and September. A receptive female swells at the rear and lets the brightest males touch her. A dominant male guards a female for days, but he cannot hold every female when many come into season at once. Mating itself lasts no more than 60 seconds. Pregnancy averages 175 days, and most births fall between January and March in the wet season.

A newborn weighs about 640 grams and is almost bare, with a dark tuft on the head and spine. Mothers carry infants on the belly, and high-ranking mothers give birth more often, about every 405 days on average. Weaning comes at about 230 days. Females first give birth between four and eight years, and reach full size at seven. Males leave the horde after six and finish growing at ten. Wild mandrills live about 12 to 14 years, and captive animals 30 to 40.

Predators and threats

The leopard is the main predator, and mandrill remains turn up in leopard droppings. Crowned eagles take the young, and African rock pythons and chimpanzees may take others. When shown a model leopard, a horde climbs trees; shown a model eagle, it hides in cover. The dominant male does not run from either, and he paces and watches the leopard. Alarm calls come more often for leopards than for eagles.

Parasites include gut worms and protozoa, tumbu fly larvae under the skin, ticks from grassland, malaria and the eye worm Loa loa. Wild mandrills carry their own strain of SIV, and some have tested positive for enteroviruses and a human astrovirus. The gravest threat is people. Hunters kill mandrills for bushmeat, and their loud calls make them easy to find. Logging and farming have destroyed much of the forest in Equatorial Guinea and southern Cameroon.

Population and conservation

The IUCN listed the mandrill as Vulnerable in 2019. The total population is unknown, but it is suspected to have fallen by more than 30 percent over 24 years. Where hunting is heavy, in Cameroon and Equatorial Guinea, groups seem to have shrunk. The status of the Congolese population is unknown. Gabon, with few people and vast forest, is the best hope for the species.

CITES Appendix I bans commercial trade in wild-caught mandrills. The African Convention lists it in Class B, which protects it but allows killing under special permit. Each range country has at least one protected area with mandrills. Gabon has leased most of its forest to timber companies, but about 10 percent lies in national parks, 13 of them created in 2002. A semi-wild colony lives at the medical research centre in Franceville, Gabon.

Relationship with humans

In its range the mandrill is meat. Bushmeat hunting is commercial as well as local, and the species is a prized catch. Mandrills raid oil palm plantations and, when food is short, farm crops. Wild animals also share viruses with people, and a human astrovirus has been found in them.

Far from Africa the mandrill is a zoo star. It lives long in captivity, and one female was still alive at 40. Zoo mandrills steal glasses and pipes from visitors, and Zurich Zoo had to glaze its enclosure for insurance reasons. Research colonies, above all the one at Franceville, have probably taught science most of what it knows about mandrill rank, colour and scent.

In culture and myth

Europeans met the mandrill before they understood it. Gessner, in the sixteenth century, drew it as a hyena, and Pennant called it the ribbernosed baboon. Charles Darwin, in The Descent of Man, judged the adult male mandrill the most extraordinarily coloured mammal of all. Its Chinese name, shanxiao, is the name of a mountain spirit in Chinese folklore, which probably reflects its strange face.

In Western popular culture the best-known mandrill is Rafiki, the shaman of Disney's The Lion King. Rafiki lives in a baobab, advises the lions of Pride Rock and speaks with a West African accent. His name means friend in Swahili. The animators gave him a long baboon tail, which a real mandrill lacks, and many viewers still call him a baboon. This page found no recorded African myth about the mandrill, though the forest peoples of Gabon probably have their own stories.