Developing a biomimetic acoustic deterrent to reduce bat mortalities at wind turbines

Abstract

High bat mortalities at wind turbines have emerged as an unexpectedly severe environmental impact of developing wind farms all over the world, motivating an urgent need to develop effect deterrent strategies that can be implemented efficiently on a large scale. Echolocating bats use ultrasonic sonar to navigate, and some studies have shown that broadband ultrasonic noise can have a deterrent effect under certain conditions. Thus, ultrasonic noise may be an attractive approach, but attempts to incorporate electronic sound generating solutions have generally failed because of insufficient bandwidth and intensity as well as their sensitivity to the harsh environmental conditions. To get around these constraints, we designed a biomimetic whistle loosely modeled after the bat larynx that could be mounted on the moving turbine blades to passively generate ultrasonic sounds tuned to the acoustic parameters of bat’s auditory system. The whistle produces multi-harmonic tones detectable by the most impacted bat species from distances approaching 100 me away. To test whether the whistle actually deters bats or alters their flight paths, we conducted a series of playback studies in the lab and field using microphone arrays and videography. This presentation will focus on the results of these behavioral studies assessing whether or not bats change their flight trajectories in response to hearing the acoustic stimulus produced by the whistle.