Anthropogenic Effects on Bat Activity and Diversity along the Eerste River, South Africa

We investigated the effect of anthropogenically-driven habitat modifications on insectivorous bat activity and diversity along a stretch of the Eerste River, Stellenbosch, South Africa, by determining insect abundance, water quality and vegetation and river characteristics at four sites of varying anthropogenic impact. Passive acoustic monitoring was used to determine species composition and activity of bats at each of the sites. A total of 14,457 bat passes was recorded, with the same six species being found at each of the sites: four clutter edge foragers (Myotis tricolor, Eptesicus hottentotus, Miniopterus natalensis and Laephotis capensis) and a single clutter forager (Rhinolophus clivosus) and open-air forager (Tadarida aegyptiaca). Bat activity was greater at the lower two most eutrophied sites, and greatest at the residential (urban) site. Laephotis capensis, an urban-adapted species, was by far the most active, probably on account of both insensitivity to light pollution, and roost-site availability. The highest and most pristine site (Eiland) and the lowest and most polluted site (Spier) displayed the greatest diversity, despite highly elevated levels of chloride and nitrate at the latter site. So anthropogenic effects on water quality appear not to have negatively affected bat diversity along this stretch of the Eerste River. As these effects are likely to increase, this study serves as a baseline for future monitoring of bats along its course.