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January 21, 2022

New research published in a Special Issue of the Journal Animals advances our knowledge of the interactions of bats with wind turbines. Scientists lay the groundwork for new ways to assess risk and potential impacts from land and offshore wind energy to whole populations of migratory tree-roosting bats.  

Wind energy provides a viable path towards climate change mitigation by replacing fossil fuel-based energy sources that emit greenhouse gases. One unintended consequence of wind energy, however, is that hundreds of thousands of bats die from collisions with wind turbine blades annually in North America according to studies published in 2012.  

USGS scientists are developing solutions that can reduce fatalities to these flying animals, working towards the broader goal of helping our Nation maintain a rich biodiversity of species as wind energy grows across the landscape. The Special Issue focuses on advances in technology for observing bat activity and behavior at wind energy sites, and physiological characteristics that relate to how bats respond to various stimuli (light and sound) that attract or deter bats to wind turbines. 

 

A thermal image video shows a bat (small orange object in upper left) flying close to a wind turbine blade (long yellow vertical structure) approximately 150-180 feet above the ground. The red and blue slow-moving clumps are clouds above (Paul Cryan, USGS).

 

Deterring Bats from Approaching Wind Turbines  
Bat, bird, and insect activity can be monitored with pairs of thermal-imaging cameras mounted on the wind turbines (a), and automatically recorded to a computer inside the base of the turbine (b). (From Cryan et al., Animals 2022, 12(1)
Bat, bird, and insect activity can be monitored with pairs of thermal-imaging cameras mounted on the wind turbines (a), and automatically recorded to a computer inside the base of the turbine (b). (From Cryan et al., Animals 2022, 12(1))

The reasons why tree bats fly towards wind turbines and sometimes collide with the blades remain a mystery to bat biologists and wind energy developers. Although technologies are being designed and tested to deter bats from approaching wind turbines, measuring their effectiveness is challenging.

In a collaborative research project with the U.S. Department of Energy and the National Renewable Energy Laboratory, the team experimentally lit a wind turbine at night with a dim, flickering ultraviolet (UV) light while measuring the presence and activity of bats, birds, and insects with thermal-imaging cameras. Although UV treatment did not significantly change bat, insect, or bird activity, the reliance of bats on sound- and light-based cues as they approach wind turbines at night suggests that further exploration of light-based deterrence systems for reducing fatality may be warranted. This research shows that thermal surveillance cameras may serve as a tool for observing bat behavior and for evaluating the effectiveness of new technologies intended to deter bats from approaching wind turbines.  

 

Impacts to Bats Flying Offshore 

Some North American tree bats make long migrations to overwinter in more southerly latitudes or coastal regions where they day-roost in trees and have been observed flying offshore during spring and fall migration periods. To help assess the potential risk to bats from planned offshore wind energy, which is not yet unknown, researchers tracked bat movements using acoustic recorders placed on structures such as lighthouses off the coast of Virginia.  In this study, the researchers found that bat visitation offshore or to coastal barrier islands at night is associated with wind speed, temperature, visibility, and time of year.  They then used the data collected to develop a tool to predict occurrence of bats at potential future offshore wind sites. This information can help the offshore wind industry plan for strategies to minimize collisions with bats flying offshore.  

 

Impacts on Bat Populations 
A VaTech student is holding a Hoary bat captured in a mist net during the summer of 2017 at Prince William Forest Park in VA.
Hoary bats get their name from their long, dense fur with white tips that give them a frosted or “hoary” appearance.  Hoary bats are a rare treat in researcher’s mist-nets due to their propensity for high altitude flight. In this picture a VaTech student is holding a Hoary batcaptured in a mist net during the summer of 2017 at Prince William Forest Park in eastern VA as a part of her PhD research at Marine Corps Base Quantico and Prince William Forest Park. 

Bats are elusive, making it difficult for researchers to measure their population status.  It remains unclear whether mortality of bats from collisions with wind turbines is affecting their population trends and potentially threatening their persistence in the long term. This article reviews acoustic and genetic methodologies to assess changes in bat populations, which is important for understanding the cumulative impacts and resilience of bats to a variety of threats. Acoustic and genetic techniques may help improve our understanding of the population status and trends of bat affected by wind turbines.  

Data collected through the North American Bat Monitoring Program (NABat) and various associated efforts to understand bat genetic diversity can aid decision makers in determining species viability in the face of multiple threats.s.

 

View the Special Issue here https://www.mdpi.com/journal/animals/special_issues/bat_biology  

Additional information about USGS research on energy and wildlife can be found on this USGS website.