Drone-mounted audio-visual deterrence of bats: implications for reducing aerial wildlife mortality by wind turbines

Wind energy is a major and rapidly expanding renewable energy source. Horizontal-axis wind turbines, the main tool in this industry, induce mortality in flying animals and consequently bring about conservation concerns and regulatory restrictions. We utilized a unique combination of RADAR, LIDAR and ultrasonic acoustic recorders to test the utility of a novel technology meant to prevent wind turbine-related mortality in bats. Our drone-mounted deterrent device produces a pulsating combination of strong auditory and visual signals while moving through the air. LIDAR was used to assess the device's impact below its flight altitude and RADAR to assess its influence above its flight altitude. Continuous acoustic recordings from ground level to similar to 400 m above-ground-level were used to monitor bat activity in the research site. We recorded the nightly altitudinal distributions of multiple bat species throughout the experiment. Analysis revealed a significant change in activity while the deterrent was flying compared to baseline conditions. We also recorded a significant similar to 40% decrease below and a significant similar to 50% increase above the deterrent's flight altitude during its operation compared to the post-flight control. The tested technology is independent of wind farm activities and does not require modifying wind turbine form or operation procedures. The device differs from previously proposed solutions by being dynamic - moving in the airspace and emitting constantly changing signals - thus decreasing the probability of animal habituation. Our findings suggest that the deterrent could dramatically decrease wind turbine-related mortality by deterring bats from approaching rotor-swept airspace. Focused implementation in conditions where bat activity and energy production are in conflict may provide a practical, cost-effective mortality mitigation solution compared to current alternatives. Thus, our results should be considered by the wind-turbine industry and environmental monitoring and animal conservation organizations, as well as by regulatory agencies, when pursuing alleviation of wind turbine-related mortality.