This species has a pronounced sexual dimorphism. Males are almost twice as large as females and have impressive upper canines that can measure more than 6cm, which they bare to threaten rivals or predators. Their faces and hindquarters are vividly coloured; the higher the individual ranks in the hierarchy, the brighter the colouring.
 
In the wild, Mandrills live in large groups of 30–49, but they can also form ‘troupes’ of up to 600! Group hierarchy is strict: the dominant male has exclusive mating rights with the female from his harem. Confrontations with other males challenging this can be violent.
 
Mandrills mainly eat at ground level and the lowest levels of the tropical forest but spend the night in the trees, out of reach of predators.
 
In the last few years, Mandrill numbers have plummeted. This is partly due to the destruction of their habitat but mainly to being hunted for their meat. Unfortunately, they are easy to find in the forest because of their constant grunting and noisy cries.