But if there is danger, he moves to the front. Some harems may include 2 or more subordinate males. These are duller in colour and are slimmer. The presence of the dominant appears to suppress the maturity of sons. Males rarely live alone, these are usually older individuals, probably ousted from their harems.
Drills are noisy, regularly grunting and screaming.
Group members keep in contact with each other while foraging through loud conversations of grunting and crowing calls. They also alert each other of predators. A drill male's threat gesture is impressive including abruptly thrusting their head forwards, retracting their eyelids, puckering up their lips and raising the crest of fur on their heads. Both drill and mandrill males have chest glands which they regularly rub branches and tree trunks with. This scent helps to maintain the dominant male's aura.