MANDRILL

Mandrillus sphinx

Geographic Distribution and Habitat

The largest of the world’s monkeys, mandrills are native to the west coast of Central Africa. These striking primates reside in the tropical rainforests, forested upland slopes, dense secondary forests, and thick bush of southwestern Cameroon, western Gabon, Equatorial Guinea, and southwestern Congo. They also live in gallery forests adjacent to savannas, rocky forests, riparian forests, freshwater swamp forests, and stream beds. 

Their distribution is bounded by the Sanaga river to the north and the Ogooué and Ivindo rivers to the east. Some researchers have suggested that mandrill populations north and south of the Ogooué might be a subspecies, given their genetic differences from the mandrill populations bounded by the Sanaga and Ivindo.

Mandrill geographic distribution. Map: IUCN, 2019

Size, Weight, and Lifespan

The male mandrill inhabits a much larger body and sports more girth than his daintier female counterpart. Average length in males is 30 to 37 inches (75 to 95 cm); average length in females is 22 to 26 inches (55 to 66 cm). Shoulder height while on fours ranges from 22 to 26 inches (55 to 65 cm) in males and 18 to 20 inches (45 to 50 cm) in females. Males weigh between 42 and 82 pounds (19 to 37 kg); however, the most rugged of males can weigh up to 119 pounds (54 kg). Females are about half the size of males, weighing between 22 and 33 pounds (10 to 15 kg).

In the wild, mandrills live for 20 years. In captivity, this popular zoo inhabitant can live up to 31 years; the longest recorded lifespan for a captive mandrill is 46 years.

Appearance

Flamboyant is an apt descriptor for this colorful Old World monkey, particularly the male whose colors are more vibrant than those of his female counterpart. This difference in gender coloration within a species is called sexual dichromatism, an aspect of sexual dimorphism which recognizes differences in appearance. Size is another aspect of sexual dimorphism. As noted, male mandrills are considerably larger than females. To point, sexual selection is a strong driver in mandrills. It is his commanding size and vibrant colors, particularly his brightly colored genitals, which allow the male mandrill to confidently declare his identity and virility to attract the female of his species.

Both male and female mandrills have long limbs proportional to their compact bodies, which are covered by a brownish olive-colored fur coat with a paler undercoat, white tufts, red hair patches above the eyes, and a yellow beard. Each has a stubby, upright tail. The canine teeth in males can be more than 2.5 inches (6.5 cm); for females, 0.39 inches (1.0 cm).

But it’s the mandrill’s distinctive face, and rump, that enthrall. A bright red stripe, framed by ridged blue flanges, blazes from between the mandrill’s close-set eyes down the middle of an elongated muzzle, encircling the nose, area surrounding the nostrils, and the lips.

To the mandrill’s naked rump, nature has added even more splashy color, painting it with bright hues of red, blue, and purple. The mandrill’s genitals are also colored red.

When mandrills become excited, the coloring on their buttocks further brightens. And when a female flashes her bright rump at a male, it is typically a sign that she is in estrus and receptive to mating. However, rump flashing can also be an indication of submissiveness in both sexes, particularly between subordinate and dominant mandrills, and is considered a gesture of proper etiquette.

​Diet

Mandrills are omnivores, meaning that they eat both plants and animals. They prefer fruits; however, they will also dine on seeds, leaves, and stems. Mandrills consume over one hundred species of plants. Their diet is supplemented by ants, termites, spiders, and scorpions. Also on their menu are eggs, birds, tortoises, frogs, porcupine, rats, and shrews. Opportunistic, mandrills will make use of their impressive canines to kill, with a bite to the neck, small forest-dwelling antelopes when this meal item unwittingly presents itself.

Behavior and Lifestyle

Mandrills are mostly terrestrial; that is, they spend the majority of their time on the ground, covering terrain by walking on the toes of all four limbs in what is known as digitigrade quadrupedalism. Daylight hours are spent foraging and eating. Mandrills will feed as high as the forest canopy; opposable thumbs permit them to grasp tree branches.

Come evening, mandrills seek overnight shelter in trees. They frequently change their sleeping nests to avoid detection by predators, who include leopards, crowned eagles, and the African Rock Python.

Fun Facts

The word “mandrill” means “man-ape.”

In the movie The Lion King, the character “Rafiki” is a mandrill.

Mandrills have built-in pouches in their cheeks that conveniently allow them to store snacks.

Daily Life and Group Dynamics

Mandrills live in multi-male/multi-female groups, averaging about 40 members including their young, within an even larger group called a troop. A troop can include as many as 600 to 800 individuals.

Each group within a troop is headed by a dominant male, who, in this harem society, mates with multiple fertile females and fathers virtually all the infants in his group. After mating season, males stray from their groups, earning the reputation as solitary creatures. They return if trouble threatens their harem, however, and again when it is time to breed.

Communication

Mandrills’ complex communication includes vocalizations and posturing. Exposing their teeth with their lips slightly lifted, accompanied by occasional chatter, is an indication of friendliness and a state of contentment. Conversely, when mandrills are angered they slap the ground violently and engage in staring contests while nonchalantly scratching their forearm or thigh. When unable to perform a desired activity such as mating or fighting, mandrills yawn. Yawning is also part of the mandrill’s threat repertoire: the formidable primate spreads its arms, lowers its head, and in a menacing fashion, flashes its powerful canine teeth.

During grooming (a popular pastime among family members), mandrills emit smacking sounds— similar to sounds made during copulation. A high-pitched crowing sound accompanies feeding time. To convey their location to one another in the forest, mandrills use various grunts, roars, and screams. A troop of mandrills is an extremely loud bunch.

They also use scent marking, tactile activity, and visual signals to communicate.

Reproduction and Family

Females perform most of the child-rearing. Alloparenting—child care that is provided by individuals other than the parents—exists among mandrills. So the female providing child care might be a female relative and not the biological mother.

Ecological Role

As a primate species that eats fruits and seeds, mandrills help disperse seeds throughout their habitat, which is critical to forest maintenance. Seed dispersers help trees and plants regenerate the rapidly disappearing forest.

Conservation Status and Threats

Mandrills are classified as Vulnerable by the International Union for Conservation of Nature (IUCN, 2016), appearing on the IUCN’s Red List of Threatened species. This means that the population is likely to become Endangered unless the circumstances threatening its survival and reproduction improve.

The biggest threat against the mandrill is hunting, which has led to a dramatic decline in the population. In this lucrative and illicit business, hunters use high-powered rifles and dogs to take down the colorful primate, whose flesh (bushmeat) is considered a delicacy.

Deforestation has also taken a toll on the mandrill’s habitat.

Conservation Efforts

Overall, this species is poorly protected. Although international trade of the mandrill is prohibited by the Convention on International Trade in Endangered Species (CITES), this ban is difficult to enforce.

But there is hope.

Since establishing the Congo Mandrill Project in 2013, the Jane Goodall Institute has been reintroducing rehabilitated mandrills, those confiscated from poachers, into Conkouati-Douli National Park in the Republic of Congo. The program tracks the mandrills after release to ensure that they are adapting to their new environment.

Additionally, the Wildlife Conservancy Society (WCS) is working to develop mandrill-based tourism. WCS’s efforts are based at Lopé National Park. Efforts include training and recruitment of ecoguides from the local villages and radio-collaring individual mandrills to help locate the groups. To reduce the threat of poaching, WCS provides assistance in anti-poaching and surveillance monitoring.

Education and local awareness are huge components in protecting the mandrill. By exposing the bush meat trade as unnecessary and unethical and teaching children to live in an ethically sustainable way, conservationists hope to eradicate the bush meat trade in future generations.

References:
  • http://animaldiversity.ummz.umich.edu/accounts/Mandrillus_sphinx/ 
  • http://www.newworldencyclopedia.org/entry/Mandrill 
  • http://programs.wcs.org/gabon/Wildlife/Mandrills.aspx
  • http://animals.nationalgeographic.com/animals/mammals/mandrill/
  • http://www.arkive.org/mandrill/mandrillus-sphinx/
  • https://en.wikipedia.org/wiki/Mandrill
  • https://www.researchgate.net/publication/231868842_Learning_from_the_first_release_project_of_captive-bred_mandrills_Mandrillus_sphinx_in_Gabon

Written by Kathy Downey, March 2016