Some black and white monkey males eventually take over their own harem and create a new birth group. There is no true leader of a group, but strong males usually take leadership roles. There are definite indications of infanticide in consequence of the threat of male replacements within mixed groups. Additionally, displays of their white fringe fur flapping up and down serve as warning to other monkeys. Some groups, however, do share water holes and other essential resources.
Male guerezas roar loud nocturnal and dawn choruses as a means of spacing groups.
They are most abundant in secondary forests or along rivers. They tend to live in the lower part of the trees if their area does not overlap with that of any other group of monkeys. When trees are not densely spaced, guerezas feed and travel on the ground. For example, studies have been performed that test for certain behavioral responses when the territory of a guereza group is threatened. Other studies deal with how phenotypic variability is inversely related to selection intensity.