The Udzungwa red colobus lives in multi-male, multi-female groups of anything between 7 and 83 individuals, but usually of around 24 (2) (7). Groups in highly degraded forests where food is scarce are thought to adopt a system of ‘fission-fusion’ society, in which the larger troop breaks up into smaller groups to forage (7).
The Udzungwa red colobus is a diurnal species (8) and feeds mainly on leaves, but will also eat flowers, fruits and fungi (2) (6). The peculiar behaviour of ‘geophagy’ (eating of soil) has occasionally been observed in this species, and is thought to assist digestion in a similar way to charcoal consumption by other animals (6) (9).
The Udzungwa red colobus is preyed upon by crowned hawk-eagles (Stephanoaetus coronatus) and chimpanzees (Pan troglodytes). When a predator has been spotted, these monkeys alert others in the group through a series of calls, which differ to indicate either an aerial or ground predator (2).
Information is rather scant on the reproductive biology of the Udzungwa red colobus. Males attain sexual maturity at around four and a half years of age, and females at about four, after which females are known to have a substantial pink sexual swelling during oestrus. After birth, parental care is performed solely by the female, who carries the infant on her belly for the first three months (2).