Gestation lasts for about 6 months after which females give birth to a single young. Twin young have only been observed in capivity. Infants are born with a black natal coat and pink skin, both of which endure for the first two months of life. These groups can range in size from a few head up to 50 individuals. Although the dominant male often strays from the group, he will return immediately upon any sign of danger.
Mandrills live on the ground by day and sleep in trees at night.
Their bright coloring is a key feature in social behavior. When excited, the blue color of the pad on their buttocks intensifies, their chest turns blue, and red dots may appear on the wrists and ankles. The flashing of the bright rump, which originated as a a signal of receptiveness in estruous females. has also been interpreted as an act of submissiveness in both sexes. The exposure of teeth with the lips slightly lifted, accompanied by occasional chatter, is a sign of friendliness and general well-being. When angered, mandrills slap the groung violently.