Activity of Bats (Mammalia: Chiroptera) in Coastal South Carolina: an Acoustic Study

Abstract

Coastal South Carolina has not been the focus of previous studies on distribution of bats, but the proposal of an offshore wind farm has stimulated interest in how bats use coastal areas. Anabat acoustic detectors were used to record echolocation calls of bats over wetlands in Charleston County, South Carolina, during June-October 2014 to determine if salinity of water and presence of vegetation influenced use of habitats by bats. Abundance and diversity of insects as well as environmental conditions were measured to determine if environmental conditions or availability of insects played a prominent role in where bats were active. Bats were significantly less active over wetlands with vegetation than wetlands without vegetation. Freshwater sites generally had the greatest amount of activity. However, salinity of water played a less important role in where bats were active than presence of vegetation. In addition to studying bats over wetlands, echolocation calls were recorded over barrier islands and the mainland both before and during autumnal migration to determine how activity of bats is distributed and whether there is a shift in activity by season. Islands had the greatest activity for almost all species and for overall activity of bats. Activity increased during autumn, but this was not significant for all species or groups. Neither environmental conditions nor abundance and diversity of insects appeared to play a critical role in where or when bats were active. This study implies that maintaining open-water areas devoid of vegetation is critical for managing wetland habitats to promote healthy populations of bats. Because bats were more active over islands and activity increased during autumn, which is the time when bats experience the greatest mortality due to wind farms, developers and managers of offshore wind farms along coastal South Carolina should mitigate negative impacts on bats.