What makes the blue colour on a mandrill’s face?

Neatly arranged collagen fibres in the skin

Why do mandrills groom some group mates less?

They can smell that those animals have parasites

Which mandrill sisters look most alike?

Sisters with the same mother only

Mandrill

Mandrillus

The mandrill (Mandrillus sphinx) is a big, ground-dwelling monkey from the rainforests of Cameroon, Equatorial Guinea, Gabon and the Republic of Congo. Adult males are the largest monkeys alive and among the most colourful mammals: a red stripe down the nose, swollen blue ridges on the cheeks, a golden beard and a blue-and-purple rump. Mandrills live in huge groups called hordes, which in Gabon average about 620 animals. Its only close cousin is the drill, which shares the genus Mandrillus.

Also known as Mandrillus sphinx, Mandrill Monkey

Mandrill abilities

4 of 4 new top males whose faces turned redder
A male mandrill’s red face shows his rank. When he becomes the top male his face and rear turn redder; if he loses the top spot, some of the red fades.
- Scientists followed two groups of mandrills living in big forest enclosures in Gabon. Four males rose to the top rank and four lost it.
- New top males got higher testosterone, bigger testes, redder skin on the face and genitals, and a busier chest scent gland. The blue skin did not change.
- Deposed males lost some of their red, but not all of their brightness.
- Scientists think the colours work as a signal of rank that other males can read.
Sources [3, 11, 13]
Blue + purple + red naked rump skin
A mandrill turns and shows its colourful bare rump. It is a signal: it can mean “I give in” or, from a female, “I am ready to mate”.
- The rump colours get stronger when a mandrill is excited.
- The blue comes from the same trick as the blue face ridges: ordered collagen fibres in the skin, not pigment.
- Females’ rumps are much duller, but a female’s bottom swells for about a week around the time she can become pregnant.
Sources [1, 2, 4, 14]
845 mandrills in the biggest horde counted at Lopé
Mandrills live in hordes of hundreds. To stay together in thick forest, they keep in touch with calls.
- In Lopé, Gabon, hordes filmed crossing roads and gaps averaged 620 mandrills, and one had 845. That is probably the largest stable group of any wild primate that is not fed by people.
- Scientists have described about 11 kinds of mandrill call. The two-phase grunt, the roar and crowing carry over long distances.
- Females give loud shrill screams that help the horde move together over hundreds of metres. When danger is spotted, the whole horde goes quiet.
- A count of 1,350 was once made, but the scientist later thought it was probably two hordes that had met.
How many animals in one group?
Mandrill horde, biggest845
Mandrill horde, average620
Olive baboon troop, big97
Mandrill numbers from Lopé, Gabon (1996–1999). Olive baboon troops typically hold 39–97 animals.
Sources [2, 6, 9, 27]
≈4.5 cm upper canines in adult males
A big male opens his mouth wide and shows off his long canine teeth. A yawn like this can be a threat, not a sign of sleepiness.
- Adult male canines average about 4.5 cm, more than four times as long as a female’s.
- In a long study, males fathered babies almost only while their canines were longer than about 3 cm, two thirds of the adult length.
- Canines cannot regrow. As they wear down with age, a male’s breeding days come to an end.
- A silent grin with bared teeth is different: it is usually a friendly signal.
Sources [1, 2, 3, 15]
50.7% of the Lopé diet was fruit
Mandrills stuff food into their large cheek pouches so they can eat it later, often after moving somewhere safer.
- In Lopé, fruit made up about half of the diet, followed by seeds. Leaves, pith, flowers and animal food made up the rest.
- Animal food includes insects, snails and worms. In Cameroon, mandrills were once seen catching a young bay duiker, a small forest antelope.
- When fruit is scarce in the dry season, mandrills eat more seeds, insects and leafy plants.
What mandrills ate in Lopé, Gabon (%)
Fruit50.7%
Seeds26%
Leaves8.2%
Pith6.8%
Animal food4.1%
Flowers2.7%
From 10 years of records at Lopé (Tutin et al. 1997), as summarised by Primate Info Net.
Sources [1, 2, 3, 7, 21, 22]
25 wild mandrills watched for about 2½ years
Mandrills can smell when a group member has gut parasites, and they groom that animal less. It is a way to avoid catching worms.
- In southern Gabon, scientists found that wild mandrills avoided grooming group members infected with parasites spread through dung.
- When the infected animals were given medicine and returned, they got groomed much more again.
- Parasites change the smell of dung. In tests, mandrills sniffed and then kept away from dung of heavily infected animals.
- Scientists call this “behavioural immunity”: staying healthy by choosing who to get close to.
Sources [16, 17]
Same father same face
Mandrill sisters with the same father look more alike than sisters with the same mother. Their faces may help them recognise family.
- Female mandrills grow up with sisters who share their mother and with half-sisters who share only their father.
- Scientists trained a face-recognition computer program on photos of wild mandrills. The more closely two mandrills were related, the more alike their faces were.
- Half-sisters from the same father looked more alike than half-sisters from the same mother, even though both are equally related.
- Half-sisters from the same father also spent more time together than non-relatives, so they seem to recognise each other.
Sources [18]
1 of 19 mandrill communities with this gestureStill debated
In one zoo community, mandrills cover their eyes with a hand, sometimes for more than 30 minutes. It may mean “do not disturb”.
- A scientist studied 19 mandrill communities in North America, Africa and Europe. Only one, a group of 23 mandrills, used this eye-covering gesture.
- Old and young, males and females did it, often raising the elbow high in the air.
- The habit lasted for at least a decade, even as animals died, left or were born. Group mates seemed to react to it differently, as if it meant “leave me alone”.
- Because it is found in just one group, it might be a local tradition, but that is not proven.
Sources [19]

Tap a pin on the model or a part below.

Redder after a male becomes top male
- The red stripe down the nose and the red nose tip come from skin, not fur.
- When four males in Gabon rose to the top of their groups, their faces turned redder and their testosterone went up. Males who lost the top spot lost some of their red.
- So a male’s red face is like a badge that shows how high he ranks.
Sources [2, 3, 11]
Collagen fibres, not pigment, make the blue
- The swollen ridges down the sides of a male’s snout are bright blue. That blue is not paint-like pigment: tiny, neatly lined-up collagen fibres in the skin bounce back blue light.
- A study of 34 males found that the blue makes the red stand out more against each other and against green leaves.
- The contrast between blue and red was the best clue to a male’s rank.
Sources [13, 14]
≈4.5 cm average upper canine in adult males
- Adult males have upper canines about 4.5 cm long. Females’ are only about 1 cm.
- Males fathered babies almost only while their canines were longer than about 3 cm. As the teeth wear down with age, a male’s chances of fathering young fade too.
- Wild males fight hard: of 12 males caught and checked in Gabon, only one had undamaged teeth.
Sources [2, 9, 15]
2 pouches for carrying food
- Mandrills have large cheek pouches. They can stuff food in fast and eat it later, sometimes after moving somewhere safer.
- Tap the Cheek Pouches ability to see them bulge.
Sources [3]
Orange vs white mandrill beard vs drill beard
- Mandrills have an orange to golden beard. Their cousin the drill has a white one.
- Females and young mandrills have beards too, but their faces are much less colourful than an adult male’s.
Sources [2, 3]
Both sexes rub it on things to scent-mark
- Mandrills have a scent gland in the middle of the chest. Males and females rub it on branches and other objects to leave their smell.
- New top males made more secretion from this gland; males who lost the top spot made less.
Sources [2, 11]
Blue + purple + red on a male’s bare rump
- A male’s bottom has no fur. The skin is blue to purple, with red and pink near the tail.
- The colours get more intense when a mandrill is excited. Showing the rump can mean “I give in” or, in females, “I am ready to mate”.
- Bright faces and rumps may also help mandrills keep track of each other in the dark forest.
Sources [1, 2, 3, 14]
5–10 cm tail length
- A mandrill’s tail is only 5–10 cm long, and males have slightly longer tails than females.
- An olive baboon of about the same weight has a tail around 50 cm long. A stubby tail is one way to tell the two apart.
Sources [3, 27]
3.4 × a male’s weight compared with a female’s
- The male mandrill is the largest living monkey. Adult males weigh about 32 kg, adult females about 12 kg.
- In a big study of mandrills in Gabon, adult males weighed 3.4 times as much as adult females. That is one of the biggest size gaps between the sexes of any primate.
- Females stop growing at about 7 years old; males keep growing until about 10.
Sources [2, 3, 10, 15]
2.5–15 km travelled in a day
- Mandrills walk on all fours with their palms and soles on the ground.
- Big males spend most of their time foraging on the forest floor. Females and young climb more and often feed in the trees.
- A horde can travel 2.5–15 km in a day while searching for food.
Sources [1, 2, 3]

Real mandrills

Photos from Wikimedia Commons. Some of them can repaint the 3D model.

Adult maleRed nose stripe, blue cheek ridges, golden beard, hair crest and a blue-purple rump. About 32 kg.Full grown at about 10 years; the top male is usually the reddestAlpha male: red nose, ridged snout and a thick beard (La Vallée des Singes, France). Photo: Hans Hillewaert, CC BY-SA 3.0
Blue ridges, red nose and a golden beardPhoto: Malene Thyssen, CC BY 2.5
Adult maleRed nose stripe, blue cheek ridges, golden beard, hair crest and a blue-purple rump. About 32 kg.Full grown at about 10 years; the top male is usually the reddestThe rainbow rump of a wild male in Gabon. Photo: Julien Renoult, CC BY 4.0
Adult maleRed nose stripe, blue cheek ridges, golden beard, hair crest and a blue-purple rump. About 32 kg.Full grown at about 10 years; the top male is usually the reddestA wide yawn shows off the long canines (Franklin Park Zoo, Boston). Photo: Ryan E. Poplin, CC BY-SA 2.0
A male’s skull: look at the size of those caninesPhoto: Didier Descouens, CC BY-SA 4.0
Adult femaleAbout 12 kg, a third of a male’s weight. Face black to pink with dull blue ridges; brighter around the time she can become pregnant.First baby at about 4.7 years; full grown at about 7Adult female: a dark face with dull blue ridges and no red. Photo: Hans Hillewaert, CC BY-SA 3.0
Adult femaleAbout 12 kg, a third of a male’s weight. Face black to pink with dull blue ridges; brighter around the time she can become pregnant.First baby at about 4.7 years; full grown at about 7A female walking on all fours, with a youngster behind her. Note the stubby tail (Bronx Zoo). Photo: Postdlf, CC BY-SA 3.0
A baby clings underneath an adult (ARTIS zoo, Amsterdam)Photo: Alvesgaspar, CC BY-SA 4.0
JuvenileDark face with a pinkish nose tip and an orange beard. Babies are born with a pink face.Young males leave the horde’s centre at about 6 yearsA young mandrill: dark face, no red yet (Ramat Gan Safari, Israel). Photo: TopHatRhino, CC BY-SA 4.0
Drill (genus cousin)A separate species, Mandrillus leucophaeus: jet-black face, red lower lip, white beard and ruff.The cousin: a male drill, with a black face (Limbe Wildlife Centre, Cameroon). Photo: Bernard DUPONT from FRANCE, CC BY-SA 2.0

Mandrill by the numbers

Measured by scientists in the wild and in a semi-free colony in Gabon, with comparisons you can picture.

Male weight: ≈32 kg; 31.6–33 kg on average; one source reports up to 54 kg⁠[2, 1]
Female weight: ≈12 kg; 12–12.9 kg on average⁠[2, 20]; Male32 kgFemale12 kg
Male vs female: 3.4 ×; body mass of adult males compared with females⁠[10]
Male canines: ≈4.5 cm; females about 1 cm⁠[2, 15]
Tail: 5–10 cm; males’ a little longer⁠[3]
Horde size: ≈620; average at Lopé, Gabon; up to 845⁠[6]
Horde home range: 182 km²; used by a horde of about 700 over 6 years; More than half its time was spent in under a tenth of that area⁠[8]
Pregnancy: ≈175 days; about 6 months, usually one baby⁠[20, 1]
Newborn: ≈0.9 kg; 890–906 g on average⁠[2]
Lifespan: ≈40 years; in captivity; record for the genus 46 years⁠[2, 1]

Mandrill myths and facts

Tap Myth or Fact for each claim, then check the answer.

0 of 8 answered

“A mandrill is a kind of baboon.”
“Mandrill groups can have hundreds of members.”
“The blue on a mandrill’s face is coloured by pigment, like paint.”
“A male mandrill keeps his bright colours no matter what.”
“When a mandrill yawns, it is always sleepy.”
“Grown-up males live in the horde all year round.”
“Mandrills can smell when a group member has parasites.”
“Female mandrills are just as colourful as males.”

Mandrill record breakers

Three ways the mandrill stands out among monkeys.

Largest living monkey
≈32 kg
Adult male mandrill
Adult male mandrills are the biggest monkeys alive. Male drills, their close cousins, weigh about the same.⁠[3, 2]
Biggest stable wild primate group
845
A mandrill horde in Lopé, Gabon
Probably the largest stable group of any wild primate not fed by people. Hordes there averaged about 620.⁠[6]
Huge male–female gap
3.4 ×
Adult male vs adult female mandrill
Adult males weigh 3.4 times as much as females, one of the biggest differences between the sexes in any primate.⁠[10, 15]

A mandrill’s life

Females grow up fast; males take years longer to reach full size.

Birth
A small, pink-faced baby
After a pregnancy of about 175 days, one baby weighing about 0.9 kg is born. In a Gabon colony, 61% of births came in January to March.⁠[20, 2]
About 2 months
Baby hair goes
Babies start losing their baby hair at about two months old.⁠[3]
4–8 months
More independent
In one zoo study, a baby often left its mother by 4 months and was weaned at 8 months.⁠[2]
About 4.7 years
First baby
Females usually have their first baby at about 4.7 years, long before they are full grown. Top-ranking females start earlier.⁠[20]
About 6 years
Young males move out
Young males drift to the edge of the group and leave.⁠[2]
7–10 years
Full size
Females reach adult weight at about 7. Males have a big growth spurt and reach adult weight at about 10.⁠[10]
Adult male
A few short breeding years
Males breed mostly while their canines are long and sharp. In the wild they join the horde for about three months a year, in the mating season.⁠[15, 6]
Old age
Up to about 40
In captivity, mandrills can live to about 40, and the record for the genus is 46 years.⁠[2, 1]

Mandrill vs drill vs olive baboon

Three big, dog-faced monkeys that people often mix up.

Mandrill vs drill vs olive baboon
	Mandrill	Drill	Olive baboon
Scientific name⁠[2, 27]	Mandrillus sphinx	Mandrillus leucophaeus	Papio anubis
Male face⁠[2, 27]	Red nose stripe, blue ridges, orange beard	Jet black with a red lower lip, white beard	Dark grey to black skin
Tail⁠[3, 23, 27]	Stubby, 5–10 cm	Stubby, 5–8 cm	Long, about 50 cm
Adult male weight⁠[2, 27]	≈32 kg	≈32 kg	≈25 kg
Where⁠[2, 24, 27]	Cameroon south of the Sanaga River, Equatorial Guinea, Gabon, Republic of Congo	Nigeria, Cameroon north of the Sanaga River, Bioko Island	Across much of Africa south of the Sahara
Groups⁠[6, 2, 27]	Hordes of hundreds (average about 620 at Lopé)	Groups of about 9 to 93; a few estimated at about 400	Troops of 39–97
IUCN Red List⁠[5, 25, 27]	Vulnerable	Endangered	Least Concern

The Sanaga River in Cameroon separates mandrills (south) from drills (north).

Is the mandrill endangered?

It is listed as Vulnerable: at risk, but not yet endangered. Gabon holds the largest population.

IUCN Red List

Vulnerable (VU)

Population decreasing

Mandrills need large areas of forest, and they are hunted heavily for bushmeat. Logging and forest clearing for farms also take away their homes.⁠[5, 3, 8]

IUCN Red List, Abernethy & Maisels (published 2019).

Threats

Bushmeat hunting
Mandrills are hunted for meat, including for the commercial bushmeat trade, and sometimes for traditional medicine.⁠[3, 4]
Logging and farming
Illegal logging and forest clearing for agriculture break up the forests mandrills depend on.⁠[3, 4]
Needs a lot of space182 km²
One horde of about 700 used 182 km² of land over 6 years, so protected areas must be big.⁠[8]
Human diseases
As settlements grow into the forest, diseases from people become more of a risk.⁠[4]

What’s helping

Trade ban
Mandrills are on CITES Appendix I, which bans international trade in them.⁠[1, 4]
Protected forests
Lopé National Park in Gabon protects some of the biggest hordes known, and is where many of the horde studies were made.⁠[6, 8, 9]
Long-term research
Studies in Gabon, from radio-tracking wild hordes to decades of records on a semi-free colony, show what mandrills need.⁠[8, 20, 16]

Mandrill cousins

DrillEndangered
Rarer than the mandrill: about 4,000 mature drills on the mainland and about 600 on Bioko Island. Bioko drills in lowland forest eat about 90% fruit, but in mountain forest mostly pith, leaves and fungi.⁠[25, 24, 26]
Olive baboonLeast Concern
A widespread look-alike with a long tail.⁠[27]

Mandrill quiz

12 questions. Every answer is somewhere on this page.

Question 1 of 12Score 0

What is a big group of mandrills called?

Mandrill field notes

Diet, food web, safety and badges from the Snappit field guide.

Diet & Feeding

Mandrills are omnivores, eating fruits, seeds, insects, and even small animals.

Primary Foods

Fruits
Seeds
Insects
Leaves
Fungi
Small invertebrates
Foraging Method: Foraging

Ecological connections

leopardEaten by
Leopards are a primary natural predator of mandrills.
humanEaten by
Humans hunt mandrills for bushmeat and traditional medicine.
strangler figDepends on
Mandrills frequently feed on the fruits and leaves of fig trees.
driver antEats
Mandrills consume various ant species, including driver ants.

Safety

Danger 3/5 · Moderate

Mandrills are wild animals and should be admired from a distance.

Traits

Collections

Mammals

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Cercopithecidae
Genus: Mandrillus

Sources for these mandrill facts

27 studies and references · checked Oct 29, 2026

Frequently Asked Questions

How to identify Mandrill?

Compare ears, muzzle, tail, feet and coat markings. Size is hard to judge without something nearby for scale, and young mammals may not have adult coloring yet. Mammal Identifier: upload a photo and compare the visible details.

How long is Mandrill?

60-95 cm

How much does Mandrill weigh?

10-37 kg

How long does Mandrill live?

20-30 years

What does Mandrill eat?

Mandrills are omnivores, eating fruits, seeds, insects, and even small animals.

Where is Mandrill usually found?

Forests

How does Mandrill hunt?

Foraging

Is a mandrill a baboon?

Not quite. Mandrills were once grouped with baboons in the genus Papio, but they now have their own genus, Mandrillus, shared only with the drill. An easy clue: mandrills have a stubby tail of 5–10 cm, while an olive baboon’s tail is about 50 cm.

Why are mandrills so colourful?

The colours are signals. A male’s red face gets redder when he becomes top male and fades if he loses that rank. The blue makes the red stand out, and the blue–red contrast is the best clue to rank. Females’ faces get brighter around the time they can become pregnant.

Is the mandrill the biggest monkey?

Yes. The adult male mandrill is the largest living monkey, at about 32 kg. Females are much smaller, about 12 kg. Male drills weigh about the same as male mandrills.

How big are mandrill groups?

Huge. In Lopé, Gabon, hordes averaged about 620 animals and the biggest had 845, probably the largest stable groups of any wild primate not fed by people. Adult males join only in the mating season.

What do mandrills eat?

Mostly fruit and seeds, plus leaves, pith, flowers, insects and other small animals. They store food in large cheek pouches to eat later.

Are mandrills dangerous?

They are wild animals with very long canines: about 4.5 cm in adult males. A wide yawn that shows those teeth can be a threat. Watch them from a safe distance and never try to touch one.

What is the difference between a mandrill and a drill?

Both are in the genus Mandrillus. Male mandrills have a red-and-blue face and an orange beard; drills have a jet-black face, a red lower lip and a white beard. The Sanaga River in Cameroon separates them: mandrills to the south, drills to the north.

Are mandrills endangered?

The IUCN Red List lists the mandrill as Vulnerable, mainly because of bushmeat hunting and forest loss. Its cousin the drill is Endangered.

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