Effects of forest degradation on bats at the South and North Nandi Forests, Western Kenya

Abstract

Habitat loss and degradation pose significant threats to biodiversity, especially in tropical regions characterized by high biodiversity levels and elevated deforestation rates. However, there is a lack of sufficient information concerning the effects of such disturbances on bats (Mammalia: Chiroptera) in tropical Africa. This research investigated the impact of habitat degradation on bat communities in two forests of varying sizes, South Nandi and North Nandi, located in western Kenya, through bat capture methods. Tree density and forest human use intensity served as predictors for relative bat abundance and species richness. A total of 6,003 bats were recorded, representing 21 species across seven families, during a comprehensive study involving 5,322 hours of mist-netting and 4,224 hours of harp trapping. A progressive decline in species richness (S) was observed from the forest interiors (S = 17) to the edges (S = 16) and the matrices (S = 12) at both forests. Fruit bats (n = 3427; 61.7%) were predominantly detected at the edges and within the matrices, with a limited presence in the forest interior. Conversely, forest-interior insectivorous bats and those foraging in confined spaces (n = 260; 58.6%) were primarily recorded within the forest interiors. Forest specialists exhibited significant correlations with tree density, whereas frugivores and edge- and open-space foraging species showed positive responses to human activity indicators, including cut stumps, charcoal kilns, and footpaths in highly degraded matrices and along forest edges. Consequently, specialized bat species are particularly vulnerable to habitat loss and degradation.