Mixed effects of gating subterranean habitat on bats: A review

Abstract

ABSTRACTCaves and abandoned mines, roosting environments for many bat species including subterranean obligates, are under human pressure (e.g., recreation) and pose threats to humans. Gating entrances of these subterranean features prevents human entry while protecting habitat for bats. However, bat response to these gates is not well understood and no comprehensive synthesis with species‐specific recommendations on protection measures for bat roosts exists. We reviewed literature on effects of gating subterranean habitat on bats and roost microclimate and found 22 studies and reports from North America, Australia, Europe, and Asia. Ten studies examined effects of gating on bat use, 9 described behavioral responses to gates, and 5 presented effects of gates on roost microclimate. Older gate designs (1950–1970), such as cement walls or iron doors, negatively affected bat use and roost microclimate, but responses to modern (1970s to present), bat‐compatible gate designs varied. Short‐term responses of bats to bat‐compatible gates were negative and included increases in energetically expensive flight behaviors. Although long‐term responses included a mix of population and species trends, we attribute these mixed responses in part to differences in flight agility among species. Bats with moderate to high agility (low wing loading, broad call bandwidths) adjust to gates, but species with low agility (high wing loading and narrow call bandwidths) may abandon sites after gating. Other factors including bat density in roosts and size of the cave or mine entrance also affect acceptance of gates and should be considered in gate design. Current gate designs are adequate for most species. Based on available literature, we recommend use of bat‐compatible gates with horizontal bar spacing of 14.6 cm, bar types that offer high structural rigidity in areas where vandalism is likely, and periodic monitoring of gates to ensure they remain in good condition. © 2017 The Wildlife Society.