Description

The Tana River mangabey (Cercocebus galeritus) is a highly endangered species of primate in the family Cercopithecidae. Some authorities have included the taxa agilis and sanjei as subspecies of this species, while others award these full species status.

It is endemic to riverine forest patches along the lower Tana River in southeastern Kenya. It is threatened by habitat loss and degradation, which has increased in recent years. This species was, together with the equally endangered Tana River red colobus, the main reason for the creation of the Tana River Primate Reserve in 1978,bbut human encroachment within this reserve continues.Recently, it has been suggested that 20,000 hectares of the Tana River Delta should be transformed into sugarcane plantations, but this has, temporarily at least, been stopped by the High Court of Kenya 

Fun Facts

The Tana River mangabey is diurnal and semi-terrestrial. It spends most of its time on the ground but is still considered arboreal due to its sleeping area. The species sleeps in trees which are approximately 27-37m in height which have a sparse canopy cover of 25-60%. The primate sleeps in the forks of the branches of these trees or near the main trunk. It is believed to sleep in trees to reduce the risk of predation and chooses this site according to its last feeding position in the area.

Group size ranges from 13-36 individuals, and sometimes combining to form aggregations of 50 to 60 individuals. These groups consist of multiple males and multiple females. The species have an average day-range length of 1.25 km. During the dry season when food is limited groups maintain discrete territories with minimal overlapping. To maintain these territories males give spatial vocalizations and territorial displays at fixed boundaries. The males within the group may also engage in active combat with outside group leaders invading the territory.

In the wet season when food is abundant boundaries are broken down. Foraging ranges for different groups extend and there is considerable overlap between the different groups. During this time groups are more tolerant of one another and meet and intermingle. The Tana River mangabey has a few predators, such as Python sebae, crowned eagle, martial eagle, and Nile crocodile.