Effects of lunar phase and temperature on bat activity and species richness at varying altitudes in the Kunene Region, Namibia

Bat activity and species richness patterns are often used to assess bat population trends. Understanding how environmental conditions affect bat activity is thus important for bat conservation, but understudied across much of Africa. To address this information gap, we examined the effects of environmental factors (i.e. lunar phase and ambient temperature) on bat activity and species richness in the northern Namib Desert, Namibia. From May 2016 to March 2017, we deployed long-term acoustic detectors at three locations of varying altitudes to record bat activity and captured bats to confirm species identities once per month. In total, we recorded 5865 passes from six bat families, with Vespertilionidae and Molossidae occurring at all sites. Lunar phase did not significantly affect activity on full moon versus new moon nights. Bat activity generally peaked at all sites in the early evenings independent of lunar phase, suggesting that foraging just after sunset may be adaptive. Ambient temperature had a negative effect on bat activity at all sites and bats were not active when temperatures were >35 degrees C or <= 11 degrees C, but bat activity peaked during the summer months. Despite differences in temperatures across sites, community composition was not related to altitude. Long-term monitoring of desert bat activity and species richness is important not only for addressing large knowledge gaps about the population trends and behaviours of these Namibian species and about bats in arid landscapes more generally, but also for informing local bat conservation efforts across a range of environmental conditions.