A rather terrestrial species, the sooty mangabey spends the majority of its time on the forest floor, although it will also climb up into the trees (7). On the forest floor, the sooty mangabey forages primarily for fruit; its large, strong incisor teeth enable it to eat not only the sweet flesh, but also the hard kernels and nuts (4). However, it will also consume many parts of plants found growing in swamps and the seeds of grasses, and will frequently raid farms, including rice paddies, where it feeds on crops causing significant damage (2).
Mangabeys typically live in large groups, each containing several adult males (4). In captivity, young were born at any time of the year, but births were more common between October and March (9), after a gestation period of around six months (4).