A New Population of De Brazza's Monkey in Kenya

Abstract

Until recently, de Brazza's monkey (Cercopithecus neglectus) was not known to occur east of the Great Rift Valley in Kenya. However, after eight months of intensive surveys in the remote and isolated Mathews Range Forest Reserve of Samburu, we were able to count a total of 162 de Brazza's monkeys in 24 groups; including 139 adults and sub-adults and 23 infants. They were found in ten separate laggas distributed throughout the mountain range, with the highest concentration in the central part of the reserve. By extrapolating information gathered on this study—from interviews and field observations—the population of the entire Mathews Range Forest Reserve was estimated at 200–300. Although the threats arising from the human activities in the forest ecosystem are generally minimal, they were considerable on the lower elevations, affecting especially this species. The most affected habitats are those near human settlements on the lower altitudes (where 75% of the total population of de Brazza's monkeys occurs) since they are easily accessible. During the onset of the dry season and periods of drought, communities invade these areas with large herds of livestock, where they feed them on leaves of evergreen tree species such as Faidherbia albida, Ficus sp., and Olea sp. The people cut the branches almost denuding the tree. These species are important in the diet of de Brazza's monkey. The study resulted in the first record of de Brazza's monkeys occurring above 2,100 m above sea level. They were seen in Olkaela in the Mathews range at an elevation of 2,203 m.