The mandrill is the largest monkey on Earth, and arguably the most colorful mammal.

Nature · Published 3 October 2026 Swipe more like this →

In short: With vibrant blue and violet cheeks, a scarlet nose, and crimson hindquarters, the male mandrill is a visual spectacle. Beyond its striking appearance, this stout-bodied primate holds the title for the largest monkey species, living in complex, elusive troops deep within the rainforests of equatorial Africa.

The mandrill, scientifically known as Mandrillus sphinx, is a ground-dwelling primate native to the rainforests stretching from the Sanaga River in Cameroon down to the Congo River. Adult males are formidable, reaching up to 35 kilograms and 90 centimeters in length. They display intense sexual dimorphism, with males possessing far more vivid facial and rump coloration than the considerably smaller females, who average about 13 kilograms. These colors are not merely decorative; the red hues result from blood vessels near the skin's surface, while the striking blue ridges are a product of structural coloration created by parallel collagen fibers.

Historically misclassified as baboons, mandrills are now recognized as a distinct genus within the family Cercopithecidae. Genetic research suggests their closest evolutionary relatives are white-eyelid mangabeys, with the two lineages diverging approximately 4.5 million years ago. Despite their size and distinct appearance, they remain elusive, making accurate population counts difficult. They typically live in troops led by a dominant male, though these groups can occasionally merge into massive aggregations of over 100 individuals to travel through the forest.

The species faces significant conservation challenges, having been listed as vulnerable by the IUCN since 1978. Ecologists estimate that populations have plummeted by as much as 30 percent over the last several decades. The primary drivers of this decline are habitat loss due to deforestation and intense hunting pressure, particularly in Gabon and the Republic of the Congo, where they are targeted for the bushmeat trade. While protected areas like Lopé National Park provide some refuge, experts argue that a comprehensive census is vital to understanding the true status of these primates.

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