Tana River Crested Mangabey

The Tana River mangabey is found in the southeastern portion of Kenya along the Tana River, within 27 forest fragments along a 60 km stretch of floodplain forests. The gallery forest along the Tana River is home to several primate species - the Tana River mangabey, Tana River red colobus, blue monkey, yellow baboon, vervet monkey, and two species of bush babies. This species is restricted to riverine gallery forests in this area. The forests in which it is found are naturally fragmented due to the meandering of the Tana River and its fluctuating water levels. The forest is becoming even more fragmented due to habitat loss from human disturbance, which may reduce species' survival.

The Tana River mangabey is diurnal and semiterrestrial. It spends most of its time on the ground, but is still considered arboreal due to its sleeping area. The species sleeps in trees about 27–37 m 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 has 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 considerable overlap occurs between the different groups. …