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Illinois State researchers eye bat deaths at wind farms

NORMAL – An Illinois State University research team has helped upend a widely accepted theory that wind farms are deadly to bats because of the low-pressure field created by the turning turbine blades.

Instead, the researchers found that the most likely cause of death is traumatic injury from colliding with the blades. That theory, while obvious, came under fire in 2008 when a study suggested barotrauma was the major cause of bat deaths.

Illinois State professor and co-researcher Angelo Capparella said the team took a “CSI” approach to the question, finding in lab mice that the forensic features that pointed to barotrauma could actually be mimicked by decomposition, exposure to heat and freeze-thaw cycles. They then compared bat specimens found at a Central Illinois wind farm with specimens from a museum that were known to have hit high-rise buildings.

“The simplest explanation for all the kinds of damage that you see to a bat that’s been killed at a wind turbine is caused by, basically, blunt-force trauma,” he said.

Bats are an important part of the ecosystem, and some studies suggest that the mammals provide the equivalent of $3 billion annually in pest-control services, Capparella said.

But they haven’t adapted to having big metal structures jutting out from the middle of Central Illinois cornfields, he said. They use a sensory tool called eco-location to navigate in the dark, but only when feeding, not while migrating, he said.

“So here they are just sort of blithely moving through a cornfield at night, and suddenly – whap! They hit a turning turbine blade,” Capparella said.

He said their research could help wind farms develop better strategies for reducing those deaths. One idea: turning off the turbines during select nighttime periods when bats are most likely to be traveling through the area.

“It really wouldn’t be that many nights within the fall migratory season, when the mortality is the highest, that you’d have to turn (the turbines) off, just during the nighttime,” he said.

Illinois State graduate student Katie Rollins, who has since graduated, was a lead researcher, along with others from University of Iowa and Western EcoSystems Technology Inc. Their research was published in the March issue of the journal Veterinary Pathology.