Mandrill

The colour advertisement

The male mandrill’s face — ridged nose stripes of electric blue with a scarlet central stripe, scarlet nostrils and lips, and yellow beard — is the most intense facial colouration of any mammal. The genital and rump region is equally vivid: bright red surrounded by blue. These colours are not paint — they are structural colour produced by collagen fibres that reflect specific light wavelengths.

The colour intensity directly correlates with testosterone levels and male dominance. The most dominant male has the most intense colour. When subordinate, colour fades; when dominant, it intensifies. Females prefer the most colourful males. The colouration is thus an honest signal of genetic quality.

Largest monkey

The mandrill is the heaviest monkey in the world (as distinct from apes). Adult males can reach 37 kg — significantly heavier than the baboon, the next largest monkey. Sexual dimorphism is extreme: females weigh approximately half of males. Males have long canine teeth used in threats and combat.

Forest floor foragers

Mandrills spend most of their time on the ground in dense forest, foraging for fallen fruit, seeds, fungi, insects, and small vertebrates. They use cheek pouches to collect food while foraging and process it later. Their home ranges are very large — a horde may travel 10 km per day.

Threats

Mandrills are classified as Vulnerable due to hunting (bushmeat is a significant pressure in their range), habitat loss from logging, and capture for the exotic pet and biomedical research trades. Their dense forest habitat makes accurate population estimates difficult.