Red Bat Movement Response to an Ultrasonic Acoustic Deterrent in Flight Cage Trials: Implications for Reducing Bat Fatalities at Wind Facilities
Date
2021-08
Authors
Stamps, Brittany F.
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Abstract
Wind energy is an essential aspect of combating climate change, but it is not without risks. Bat fatalities due to wind turbine blade strikes are an unintended consequence of this renewable energy source. To date, results from strategies to reduce bat fatalities have been inconsistent among species or too expensive to implement. Ultrasonic acoustic deterrents (UADs) are designed to create a disorienting airspace around wind turbines by emitting sounds that jam bat echolocation calls; however, field tests of UADs have had variable success among species. Variability may be due to higher-frequency sounds attenuating over shorter distances or, relatedly, because bats may not encounter their characteristic frequency range at greater distances from the UAD; thus, the UAD not effectively jamming bat echolocation. Red bats (Lasiurus borealis and Lasiurus blossevillii) are of particular interest as these species are commonly reported at wind energy facilities and existing data indicates UADs are not successful at reducing red bat fatalities. My objective was to compare the effectiveness of various sound emissions from an NRG Systems-manufactured UAD at deterring red bats and compare seasonal and sex differences in responses. During July–October 2020 and March–May 2021, I individually released red bats (n = 51) into a 60 x 10 x 4.5-m (L x W x H) outdoor flight cage located in San Marcos, Texas, USA. I tracked flight using thermal video cameras during three, four-minute trials of three frequency ranges: 20–32 kHz (low), 38–50 kHz (high), and 20–50 kHz (combined), interspersed by four-minute control periods (i.e., UADs powered off). I assessed differences in distances red bats flew from UADs and compared between each treatment and the control period using Kolmogorov-Smirnov analyses. Results indicated all treatments were similarly and significantly effective compared to controls, causing red bats to vacate treated airspace to similar distances during any treatment. These results indicate low-frequency ultrasound may provide a viable option to deter red bats, as the sound does not attenuate as over longer distances; thus, may be more effective at greater distances as wind turbine blade size increases.
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Keywords
bats, chiroptera, Lasiurus, red bats, L. borealis, L. blossevillii, deterrent, thermal video, flight cage, fatality minimization, acoustic deterrent, wind energy, bioinformatics
Citation
Stamps, B. F. (2021). Red bat movement response to an ultrasonic acoustic deterrent in flight cage trials: Implications for reducing bat fatalities at wind facilities (Unpublished thesis). Texas State University, San Marcos, Texas.