On occasion, birds, eggs, small reptiles and insects. Mainly a ground dweller, but takes shelter in the trees when alarmed. Usually found in groups of 20-50. Looseness or rigidity of the dominance hierarchy varies with the particular environment and with the numbers of neighboring green monkey groups. In one sub-species, male hierarchy is so important that visual signals reinforce dominance.
All males have blue scrotums, the alpha male developing the deepest blue.
Gestation lasts 163 days. They reach sexual maturity at the age of 4 years. Record life span is 30 years. Tail is well developed and used for balance. They have a creaking cry and a staccato bark that enables members of a troop to keep in contact.