A noisy flashing drone could keep bats away from wind turbines, which kill millions of the flying mammals each year.
“When people first started to notice that animals were getting hit by wind turbines, the focus was really on birds,” says at the University of Haifa in Israel. “It took a few years longer to understand that bats were getting hit, and during those few years a lot of wind farms were being built.”
Thousands of wind turbines around the world are located in “really bad places” where they injure or kill bats, says Werber. That is a problem because bats play a crucial role in controlling local insect populations and pollinating plants.
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Werber and his colleagues set about developing a bat deterrent involving a drone with flashing lights and speakers that emit loud, high-frequency chirps encompassing the upper end of the human hearing range and beyond. During a test run in northern Israel’s Hula Valley in July 2020, bats successfully avoided the drone.
Unlike similar deterrent devices mounted on stationary poles or the wind turbines themselves, the drone’s movements and light-and-sound show are unpredictable. “We wanted it to be as random as possible and as dynamic as possible to avoid habituation where animals just get used to it,” Werber says.
To test the drone, the researchers flew it at altitudes similar to those of wind turbines and at a time and place where they knew bats were active. They also used a combination of radar and lidar to monitor the number of flying objects that were about the size of bats.
Over a three-week period, the researchers saw about a 40 per cent decline in bat activity below the drone’s flight altitude, while bat activity above the drone increased by 50 per cent. These changes in bat behaviour were detected up to 500 metres above the drone suggesting that bats were flying higher to avoid the drone’s annoying routine.
Such drones could flexibly deploy bat deterrent systems in a targeted way without requiring constant drone patrols, says , formerly at the Leibniz Institute for Zoo and Wildlife Research in Germany. But she wants to see a longer study period than the initial three-week experiment to better understand the impact on both migratory bats and bats that live in the area – not to mention nocturnal birds and insects.
“It could turn out to be one of those experiments that are great for one thing and awful for others,” says Kruszynski. It’s important to understand if the drone’s lights and sounds affect other animals in the area or cause any unexpected harm to the bats themselves, she says.
This drone deterrent system may be best suited for smaller wind farms with just dozens instead of hundreds of turbines, Werber says. But he also suggested that active detection of bats could provide targeted drone deterrence of bats even on larger wind farms – and he expects improving drone technologies for autonomous flight and recharging to make this an even more attractive idea in the next several years.
Remote Sensing in Ecology and Conservation
