The mandrill (Mandrillus sphinx) is a large Old World monkey native to west-central Africa. It is one of the most colorful mammals in the world and its closest living relative is the drill. Both species were traditionally thought to be baboons, but further evidence has shown that they are more closely related to White-eyelid mangabeys.
The mandrill has a stocky body with a large head and muzzle, as well as a short and stumpy tail. The limbs are evenly sized and the fingers and toes are more elongated than those in baboons, with a more opposable big toe on the feet. The mandrill is the most sexually dimorphic primate, and the adult male is considered to be the largest monkey. Females are less stocky and have shorter, flatter snouts. The coat of the mandrill is primarily grizzled or banded olive-brown with a yellow-orange beard and sparse, light hairs on its underside. The lips are surrounded by stiff white whiskers, and white bare skin exists behind the ears. Male mandrills have a "crest" of long hairs on the head and neck, while both sexes have chest glands which are covered by long hairs. The face, rump and genitals have less hair. Mandrills have a red line running down the middle of their face which connects to their red nose. On either side of the line, the skin is blue and grooved. In males, the blue skin is supported by ridged bone swellings. Females have more subdued facial coloring, but this can vary between individuals with some having stronger red and blue hues and others being darker or almost black. The red coloration is created by blood vessels near the surface of the skin, while the blue is a form of structural coloration caused by parallel arrangements of collagen fibers. The blue ridges on males contrast with both the red facial hues and the green foliage of their environment, helping them stand out to other individuals. The darker and more subdued coloring of female faces is caused by melanin.
The natural range of this species stretches throughout equatorial Africa, including southwestern Cameroon, western Gabon, Equatorial Guinea, and southwestern Congo. Within this territory, mandrills primarily prefer living in tropical rainforests, and patchy gallery forests surrounded by savanna and travel across grass areas within their forest habitats. They can also be found in mountainous areas, near rivers, and in cultivated fields.
Mandrills are very social animals, forming mixed groups of up to 40 individuals that, in turn, gather into large troops of over 600 animals. Individuals in these groups live in a well-defined social hierarchy. Each unit is led by the large and colorful dominant male, who mates with receptive females and fathers nearly all young in the group. A single troop can occupy a territory of up to 50 km². Since mandrills are territorial animals, the home range of each troop is scent-marked and fiercely defended against outsiders. Group members generally associate with each other through deep grunts, making a loud noise. They are known to emit high-pitched crows when feeding. Additionally, the dominant males give out a two-phase grunting call when the group has to move on. Mandrills are diurnal animals, spending most of their daytime hours looking for food and finding shelter in trees by night. Mandrills also spend a considerable amount of their active time grooming, during which they emit smacking noises, resembling those given during mating. When mandrills are in a playful mood and want to be groomed, they announce it by shaking their head and shoulders.
Being omnivorous animals, mandrills consume food of both plant and animal origin. They eat various fruits, seeds, fungi, and roots, supplementing this diet with insects, snails, worms, frogs, lizards as well as occasional snakes and small vertebrates.
Mandrills have a polygynous mating system, where the dominant male controls and mates with a group of females called a harem. Mandrills breed whenever there is sufficient food supply, usually from July to October once every 2 years. The gestation period lasts for 6 months. Females generally give birth to one infant in December-April. Some captive females of this species have been known to yield twins. The newborn infant is fed, cared and protected by not only its mother but also other females of the group such as aunts, sisters, and cousins. Mandrills are weaned within 6-12 months old, after which females continue living with their natal group, whereas, ales have to disperse at 6 years old, living along the boundary of the group. The age of reproductive maturity is 4-8 years old in females and 9 years old in males.
These primates are presently threatened by the destruction of their natural habitat due to logging, which opens the way to the remote habitat of mandrills, leading to another serious threat - hunting. Bush meat is nowadays in great demand, meeting the needs of growing populations in Africa as well as being exported to the European market. As a result, mandrills heavily suffer from large-scale hunting.
No estimate of population size is available for mandrills. Currently, this species is classified as Vulnerable (VU) on the IUCN Red List.
Due to their diet, mandrills may play some role in seed dispersal. To the extent that they serve as predators or as prey, they may have some effect on local food webs.
