Diana monkeys form groups of 15-30 with a single adult male. De Brazza's are often found in monogamous pair or one male with a few females. Where there are fewer males, a male can have more than 40 females. Males control group movement and defend the group. The social behaviour of the other members are less well known.
Daughters remain in the natal group, while males leave just before they reach maturity.
Most are threatened by hunting and habitat destruction. It is extensively hunted for it meat and skin. But the greater threat is deforestation and logging. The Mona superspecies are almost totally tree-dwelling. With long tails and strong gripping hands and feet with flexible wrists and ankles, they are very agile and fast.