They also tear live bark off the trees using their teeth and hands. When a group is feeding, the air resounds with tearing sounds and sharp cracks as they rip bark from the trees and break off dead branches to reach the insects and spiders that are hiding in the crevices. Other invertebrates are found by rustling through the broad leaves of epiphytic plants that grow on many of the big branches high in the canopy. Where fleshy fruit are scarce, they often eat a lot of nectar. They are active during the day.
All mangabeys are extremely agile climbers and excellent jumpers, but are outdone by the guenons.
Collared mangabeys forage and sleep in trees but prefer to run on the ground when attacked by predators and enemy mangabeys. The core of the group are females, led by the dominant female. One or more adult males may associate with the group. Most mangabeys are peaceful and rarely display dominance behaviour. As they forage, the group may break up into smaller groups.