Olive colobus  (Procolobus verus)

The olive colobus has the distinction of being the smallest colobus monkey (2); a group of primates that primarily consume leaves and possess an unusual stomach that enables them to digest this plant matter efficiently (4). The olive colobus has greenish-olive fur graduating to brown on the back, and dull grey undersides. The small, rounded head has a short, grey crest running down the crown with a swirl of light grey hair on each side of the forehead. A dull white ruff frames the hairless dark face (2)

The olive colobus has a discontinuous distribution from southern Sierra Leone and Guinea, through Liberia, Côte d'Ivoire, Ghana, Togo and Benin, to southeast Nigeria (2)

Inhabits forest including secondary growth within high forest, forest margins, swamp and palm forest (2).

Tree-dwelling olive colobuses live in groups of 5 to 20 individuals with around half containing one adult male with several females and their young (2), and the remaining groups having multiple breeding males (5). Members of a group communicate infrequently with very quiet chirping or burring calls (2). Little is known about reproduction in the olive colobus, but they are believed to be the only African monkey in which the mother carries her newborn in her mouth while she travels for the first month of life (6). As the infant grows, it may wrap itself around its mother's neck or cling to her body as she moves through the forest (2).

The olive colobus is a shy and retiring monkey that prefers to move through dense growth below ten metres, but climbs higher when feeding amongst the protection of other species (2) (6), particularly Diana guenons (Cercopithecus diana), which they have a strong tendency to associate with (7). By foraging with another primate species, the olive colobus benefits from extra eyes and ears to stay alert for predators (7). Males are also believed to use these associations to obtain mating partners; the Diana monkeys are a resource which they can expect female olive colobuses to visit (5). If a predator is spotted, the primary response of the timid olive colobus is to move in to dense foliage and freeze in a hunched or crouched position (2).

The diet of the olive colobus is dominated by young leaves and flowers, with 27 percent of their diet acquired from lianas, in the tangles of which they spend much of their time (8). Fruit and seeds are also eaten, with the quantities varying seasonally (2), but mature leaves are rarely ingested (8). They eat the food directly off the plant using their mouth, and do not pick it by hand (2).

Like many forest-dwelling primates, habitat loss and hunting pose the greatest threat to the existence of the olive colobus (1) (2), and populations may be declining as a result (2). However, a study revealed that the olive colobus may actually be very tolerant of hunting, but is greatly impacted by agriculture invading their natural habitat (9).

The olive colobus is known to occur in at least one protected area, the Taï National Park in Cote d'Ivoire (10), and is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that any international trade in this species should be carefully monitored (3). Otherwise, there are no known conservation measures in place specifically aimed at the rarely seen olive colobus.

For further information on colobus monkeys see:

• Macdonald, D.W. (2006) The Encyclopedia of Mammals. Oxford University Press, Oxford.

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk