Altitudinal and Seasonal Variation in the Structure of Nocturnal Primate Assemblages on Mount Cameroon

Mountain ecosystems cover a large proportion of Earth and represent important environments for a range of different taxa, including nocturnal primates. This group of primates is generally understudied because of their small size and their cryptic and nocturnal nature. Thus, much of their ecology and distribution still remains unknown, especially in mountain ecosystems. We investigated the effects of altitude and seasonality (wet vs. dry season) on observed species richness and relative abundance of nocturnal primates across the diverse forest types of Mount Cameroon. Using standardized line and recce transect methodologies, we surveyed nocturnal primates at four altitudes (650 m.a.s.l., 1100 m.a.s.l., 1450 m.a.s.l., and 2200 m.a.s.l.) on the southwestern slope of the mountain. We recorded six species (four from the Galagidae family and two from the Lorisidae family). Our results indicate a decrease in primate abundance as altitude increases. We also found that primate species composition changes with altitude. However, species diversity (Shannon diversity) drops drastically only at the highest altitude and species richness (number of species) does not differ between sites at lower to mid-altitudes. There was no seasonality effect on primate diversity. Habitat features, such as temperature, resource availability, and vegetation structure likely play a relevant role in the distribution and diversity patterns of primates on Mount Cameroon.