Guerezas generally live in small, cohesive groups, typically ranging in size from 3 to 15 individuals, but occasionally up to as many as 23 (2) (7). These social groups sometimes support several adult males, but normally comprise one adult male, accompanied by several adult females and juveniles. Despite being a diurnal species, the guereza spends over half the day resting, with the remaining hours of daylight devoted mostly to feeding and moving about. When active, this primarily arboreal species can be seen bounding through the canopy, leaping the gaps from tree to tree. The guereza sleeps during the night, with a single group generally occupying several adjacent trees nearby a source of food. To communicate, the guereza employs various vocalisations, the most distinctive of which is an impressive roar usually made by the dominant adult male and echoed by males in neighbouring groups (2). These roaring bouts, which usually take place during the night or at dawn, are thought to play a role in male-male competition and help maintain spacing between groups (2) (7).
Leaves and fruit are the main constituents of the guereza’s diet (2). In order to derive adequate nutritional value from leaves, the guereza, like other colobus monkeys, has evolved a large, multi-chambered stomach, capable of digesting enormous amounts of foliage, with the help of gut microbes that efficiently break down cellulose (2) (5) (6). The guereza itself is a source of food for several predators including crowned hawk-eagles, chimpanzees and possibly leopards (2).
Reproduction takes place at all times of the year, with the adult male, or dominant male in multi-male groups, normally having exclusive access to the females members of the group. After a gestation period lasting just over five months, the female usually gives birth to a single white-haired infant. For the first few months of an infant’s life, it is the focus of the group’s attention, and is frequently handled, particularly by the females. When moving about during this time, the infant always hangs onto the fur of its mother’s chest, but after around 20 weeks becomes more independent, and after 50 weeks no longer clings to its mother or suckles (2).