Decreased food availability can lead to aggression between groups. Mangabeys are normally a vocal group and have a variety of gestures and calls, including a loud call that can carry for quite a long way, and is used for spacing. This call is usually given in the morning. It seems like more study is needed in the area of behavior. The estrus cycle for mangabeys is roughly 30 days for all species for which data is available.
Females exhibit a pronounced sexual swelling during ovulation.
Gestation length varies somewhat, from about 167-190 days. Gray-cheeked mangabeys have a birth season, while the others do not. Pregnant gray-cheeked females develop dark red nipples and perineum. A Tana River mangabey was observed to give birth in just four minutes. Females seem to be very interested in infants, while males are less so, though captive sooty mangabeys have been observed to carry infants to protect them.