Africa's colobines the colobus monkeys are often thought of as rare, specialized forest dwellers, with limited geographical distributions, monotonous diets and dull social lives. Although some kinds of colobus monkeys are among the most localized and endangered of African primates, others are widespread and relatively common. In fact, the colobus monkeys are a diverse group of primates that display considerable ecological and social flexibility, and have some intriguing special features. As explained in Chapter 3, there are three distinct subgroups of colobus monkeys, the black-and-white, the red, and the olive. The black-and-white and red groups each contain many different forms, but how many of these merit recognition as distinct species is disputed; all authorities recognize only a single species of olive colobus, however. Although colobus monkeys are restricted to wooded habitats, they occupy a great diversity of such habitats. Until quite recently, colobus monkeys of some kind occurred throughout most of the African moist lowland forest zone, as well as in many montane forests and in gallery forests deep into the savanna zone. Even today, despite the widespread destruction of their habitats and, often, intense hunting pressure, these colobus populations occur from Senegal in the west to Zanzibar in the east, and from the Ethiopian Highlands to the southern edge of the Congo Basin. Colobus monkeys can achieve some of the highest biomasses recorded for any primates anywhere (for example, red colobus in Uganda's Kibale Forest). Their diets may be dominated by tree leaves (black-and-white colobus in the Kibale Forest), or by seeds (black colobus at Douala-Edéa, Cameroon, and at Lopé, Gabon), or may be very diverse (many red colobus populations).