Mandrill Facts: The Largest and Most Colourful Monkey on Earth

The mandrill is the largest monkey in the world and the most vividly coloured primate alive. Dominant males carry a scarlet stripe down the nose flanked by ribbed cobalt-blue cheek pads, weigh up to 37 kilograms, and bare canines longer than a leopard’s.

Mandrill at a glance

Scientific name	Mandrillus sphinx
Family	Cercopithecidae (Old World monkey)
Male weight	19-37 kg
Female weight	10-15 kg
Body length	Up to 95 cm (males)
Canine length	Up to 4.5 cm
Lifespan	20 years wild; 30-40 in captivity
Range	Cameroon, Equatorial Guinea, Gabon, Congo
Status	Vulnerable

Key takeaways

• Mandrills are the heaviest monkeys, with extreme sexual dimorphism — males can be three times the mass of females.
• Face and rump colour is testosterone-driven and tracks rank; a demoted male fades within weeks.
• They form the largest aggregations of any non-human primate, with hordes recorded above 800 animals.
• Despite the fearsome canines, they are mainly fruit and seed eaters that forage on the forest floor.
• They are not baboons — mandrills and drills were reclassified into their own genus, Mandrillus.

Why mandrills are so colourful

Charles Darwin singled out the mandrill as the most extraordinary example of colour in mammals. Modern work confirms his hunch: the red and blue face, the matching red-blue-lilac rump, and the sternal scent gland all intensify with testosterone. Females look at the face and get an honest readout of a male’s fighting ability and health, since only a male in good condition can sustain the hormone levels the colour requires. Compare with the other bright-faced species in Monkeys With Colorful Faces and Most Beautiful Monkey Species.

Hordes: the largest primate groups on Earth

Mandrill society is built on stable groups of females and young that periodically merge into vast “hordes”. Camera-trap and aerial studies in Lopé National Park in Gabon have counted single hordes exceeding 800 individuals crossing open ground — the largest gathering of primates ever recorded. Adult males are largely solitary and join hordes when females are receptive. Background in Why Do Monkeys Live in Groups?

Diet

Mandrills are omnivores with a fruit-and-seed core, supplemented by roots, fungi, bark, insects, snails, eggs, small reptiles and occasionally small antelope. They forage mostly on the ground, turning over leaf litter and dead wood, and use cheek pouches to stash food and process it later in safety. See What Do Monkeys Eat? and Do Monkeys Eat Meat?

Habitat and range

Mandrills live only in the dense tropical rainforest of southern Cameroon, mainland Equatorial Guinea, Gabon and the Republic of the Congo, bounded by the Sanaga and Congo rivers. They sleep in trees and travel on the ground, covering several kilometres a day. See African Monkeys and Rainforest Monkeys.

Conservation

Mandrills are classed as vulnerable and declining. Commercial bushmeat hunting is the dominant threat — a large-bodied, ground-travelling, loudly grunting horde is an easy target — followed by logging and agricultural clearance. Gabon’s protected area network, especially Lopé, holds the best remaining populations. See Threats to Monkey Habitats and Monkeys in National Parks.

Frequently asked questions

Is the mandrill the biggest monkey?

Yes. Dominant males reach 30-37 kg, exceeding even the largest baboons. See Largest Monkeys on Earth.

Are mandrills baboons?

No. They were once placed in Papio but are now in their own genus, Mandrillus, alongside the drill.

Why is a mandrill’s face red and blue?

Testosterone-driven pigmentation and light-scattering collagen produce an honest signal of dominance and condition.

Are mandrills dangerous?

A threatened male is genuinely formidable, with canines longer than a lion’s relative to skull size. Wild mandrills avoid people, but captive males must never be approached.

What eats mandrills?

Leopards are the main natural predator, along with crowned eagles and large snakes taking young.

Related: Strongest Monkey Species, Vervet Facts, Ultimate Guide to Monkeys.