It inhabits upland and riverine areas within tropical rainforest or tropical closed forest and is more numerous in areas containing lianas than it is in other habitats. It is arboreal but frequently descends and moves about on the ground. This species is strictly herbivorous, feeding on leaves, fruits, twigs, and bark, usually from the upper canopy of the forest. It is nocturnal, with most activity taking place soon after dark and just before dawn. The cry is made by both sexes but is much more powerful in the male, and it may have both sexual and territorial functions.
Breeding seems to continue throughout the year.
Each animal uses a small area in the forest, usually centered around a single tree. In this species both mating and birth reportedly occur during the dry season. The young are born primarily during March and April in Gabon and Cameroon and from May to August in the western and southern parts of Zaire. In the eastern parts of the range of the species, young are born throughout the year. A single baby, occasionally two, is produced after a gestation period of about 8 months.