No lunar phobia in insectivorous bats in Kenya

Abstract

We monitored foraging insectivorous bats along walked transects in forest and farmland at Arabuko-Sokoke Forest in coastal Kenya, using a heterodyne bat detector. The main purpose was to test whether aerial-hawking insectivorous bats that feed in open places (in this case mostly Scotophilus and Scotoecus spp.) show lunar phobia, i.e. restricting their activity on moonlit nights. Such behavior would be an expected response to the threat posed by visually oriented aerial predators such as bat hawks, owls and carnivorous bats. The occurrence of lunar phobia in bats is a controversial issue and may have implications for how bats will be affected by increasing light pollution. Our results show that foraging activity of the bats that we studied was related to time of day, season, and habitat, albeit with no additional effect of moonlight discernable. We therefore conclude that foraging activity occurs independently of moonlight. This result is partly at odds with previous findings including predictions from a meta-analysis of lunar phobia in bats, which indicates that lunar phobia is common in these animals, though most likely to be present in tropical species that feed in open situations near vegetation and over water. Equally, our results conform to findings from studies of aerial insectivorous bats in tropical as well as temperate areas, most of which have failed to reveal any clear evidence of lunar phobia. We believe that moonlight generally does not facilitate aerial predation on flying bats in open situations, or, alternatively, the bats accept increased predation pressure while they fulfil the energetic requirements through hunting.