Documented bat mortality at wind energy facilities indicates a significant threat to many bat populations when extrapolated out to the number of proposed installations, particularly those crossing corridors used by migrating bats. Any means of deterring bats from approaching these turbines may prevent fatal impacts. We hypothesized that selected regimes of ultrasound could generate an uncomfortable or disorienting airspace that could deter bats from entering the dangerous airspace around turbines. We tested a prototype acoustic deterrent by monitoring foraging activity at eight different pond sites during July and August in CA and OR for two nights to establish baseline activity levels, and then after observing activity similar to baseline on a third night and then activating the ultrasonic sound regime. We measured activity in the same way each night by counting “visual passes” of bats entering and leaving the recorded view from a Sony DCR-TRV520 Nightshot video camera equipped with a high intensity infrared lamp. For the same one hour period each night the mean baseline activity was 419 ±153 passes, compared to 238 ±88 passes with the ultrasound regime active, P<=0.025. We conclude that ultrasonic broadcasts have promise as a tool for deterring bats from approaching turbines and warrant further investigation and trial implementation. Not surprisingly, bats seemed most affected closer to the ultrasound emitter, suggesting that increasing the amplitude of the sound regime may increase the effectiveness and range of this approach and facilitate scaling this approach up to that required for deterring bats from the airspace surrounding wind turbines.
Preliminary Field Test Results of an Acoustic Deterrent with the Potential to Reduce Bat Mortality from Wind Turbines
Title: Preliminary Field Test Results of an Acoustic Deterrent with the Potential to Reduce Bat Mortality from Wind Turbines
August 23, 2006
Szewczak, J.; Arnett, E. (2006). Preliminary Field Test Results of an Acoustic Deterrent with the Potential to Reduce Bat Mortality from Wind Turbines. Report by Bat Conservation International and Humboldt State University. pp 7.