The dominant food choice of Colobus guereza are leaves from Celtis durandii . Young leaves of C. durandii are primarily selected, but also selected are the mature leaves of this particular hackberry tree. The trees most eaten are deciduous and at the forest edge. Analyses of chemicals in the plants eaten found that the key factor in the determination of leaves eaten is the tannin content. In captivity, the diet of the Colobus Monkey should reflect their preference for a leafy diet.
Zoos supplement the Colobus daily diet with browse.
A Colobus troop is a cohesive group typically composed of a single adult male, three to four adult females, sub-adults, a juvenile, and an infant. The size of the troop ranges from 3 to 15. Multi-male troops have been observed as well as bachelor groups of males, but both of these groupings are believed to be temporary. These troops are highly social, mutual handling of infants by members other that the mother is believed to maintain the cohesiveness of the group. Females spend a great deal of time in allo-grooming.