Changes In The Seasonal Activity Of Bats Occuring In The Kunene Region, Namibia: Influence Of Environmental Factors

ABSTRACT

The Kunene region is an arid region with extreme environmental conditions. Understanding how environmental conditions affect bat activity, number and distribution is important for assessing activity and abundance. Monthly bat activity and the effect of environmental factors (temperatures, moon phase) on bat activity were recorded to elucidate factors influencing the distribution of bats. Wildlife Acoustic SM2 detectors were used to detect the bat activity from three sites, altitudinal gradient 238 to 970 m. A total of 6893 bat calls were recorded from five families at the study sites. Two families Vespertilionidae and Molossidae appeared to be present and dominant at all sites. Bat activity was significantly higher in the summer months, community composition was not related to altitude and no endemics were found. The highest activity was recorded at Hoanib (271 m). Temperatures were measured with data loggers at sampling sites and moonlight was compared using lunar phases. Activity was positively correlated with temperature at all sites and rarely occurred when temperatures were ≤ 11°C. Moon lunar phase did not affect activity as there was no significant difference between bright and dark nights (P>0.005). Bat activity was greater at the beginning of the night, independent of the presence of the moon at all sites, indicating that foraging just after sunset is adaptive. Bats response to moonlight maybe species-specific. Study results indicate that bat activity was highest at lower altitudes with more vegetation. Such information may be useful in recognizing conservation priorities of bats in the Kunene region. As these lower altitudes are more prone to human impacts which can lead to habitat degradation due to overgrazing and denudation of large trees for firewood. Therefore long-term monitoring of bat activity in the Kunene Region is important where environmental conditions may be extreme and variable.

Keywords

Bats, activity levels, echolocation, acoustic monitoring, bat detectors