Evaluating the effectiveness of an ultrasonic acoustic deterrent for reducing bat fatalities at wind turbines

Published source details Arnett E.B., Hein C.D., Schirmacher M.R., Huso M.M.P. & Szewczak J.M. (2013) Evaluating the effectiveness of an ultrasonic acoustic deterrent for reducing bat fatalities at wind turbines. PLoS ONE, 8, e65794.
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This study is summarised as evidence for the following.

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	Deter bats from turbines using ultrasound Action Link

Deter bats from turbines using ultrasound

A replicated, randomized, controlled study in 2009–2010, with a before-and-after trial in the second year, at a wind farm in a forested area of Pennsylvania, USA (Arnett et al. 2013) found that an ultrasonic deterrent had mixed effects on bat mortality. In 2009, 21–51% fewer bats overall were killed per deterrent turbine (average 6 bats killed/turbine) than control turbine (average 9 bats killed/turbine). The difference in mortality was significant for hoary bats Lasiurus cinereus (deterrent: average 4 bats killed/turbine; control: 2 bats killed/turbine), but not for five other bat species (see original paper for data). In the 2010 before-and-after trial, between 2% more and 64% fewer bats were killed overall at deterrent turbines than at control turbines when accounting for differences found between control and deterrent turbines in the ‘before’ trial. Differences for individual species were not tested for statistical significance due to low numbers (see original paper for data). In 2009 and 2010, 10 randomly selected wind turbines were fitted with deterrent devices, and 15 randomly selected turbines without the device were used as controls. The deterrent emitted continuous ultrasonic broadband noise at 20–100 kHz. In 2009, daily carcass searches were conducted in August–October. In 2010, the before-and-after trial was conducted with daily carcass searches in May–July before the deterrent was used, followed by daily searches in July–October with the deterrent active. Carcass counts were adjusted to account for searcher efficiency and removal by scavengers.

(Summarised by: Anna Berthinussen)