This mimics a snarl and the brightness and size of these ridges indicates the male's age and condition. The whole is framed with bright orange chin and side-whiskers. The female has smaller nose ridges and a grey-black face. In this competition, males gain advantage in prominently advertising his social position and readiness to mate. This may also explain why males are more than twice the size of females.
Males also have larger canines.
The males only colour up when they reach maturity. Male average 25 kg, female 11.5kg. Mandrill males can reach 54 kg. One young, twins rare. Gestation 168-178 days, maturity at 4 years.