A State of Oregon study says wind turbines threaten bats in migration

BEND – According to a study by Oregon State University-Cascades, a bat in the Pacific Northwest that migrates south for the winter faces a severe wind threat.

The study concludes that the ashen bat is facing an uncertain future, as its numbers have decreased by 2% per year, reports the Bend Bulletin.

Collisions with propellers in wind farms kill bats, said Tom Rodhouse, one of the authors, an ecologist at the National Parks Service and a faculty member at OSU-Cascades.

Another cause is barotrauma, which occurs when bats fly over areas of low pressure created by rotating blades of a wind turbine. The sudden change in pressure causes their lungs to expand faster than bats can breathe out, resulting in exploded vessels filling their small lungs with blood, Rodhouse said.

"These direct collisions with turbines have killed millions of bats over the past two decades," said Rodhouse.

Oregon and Washington have 3,600 wind turbines with a capacity of 6,300 megawatts. Most wind farms are clustered near the Columbia Gorge. Others are found near Ellensburg and Walla Walla in Washington and Baker City Oregon.

During their migration, the gray bats travel to dangerous areas because their sophisticated sonar capabilities do not detect pressure losses, Rodhouse said.

Barotraumatites have similarities to the decompression syndrome experienced by divers. The lungs of birds are stiffer, with strong capillaries, making them less vulnerable to pressure changes near wind turbines.

The white nose syndrome, a disease that killed bats elsewhere, does not affect the ashen bat, Rodhouse said.

The ash bats bear the name of their fur coats with white ends, which look icy. They hunt at night and feed on the pests that eat the crops. The animals are slow to breed in the Pacific Northwest, with females producing only one to three cubs a year, Rodhouse said.

Cree Hein, of the National Renewable Energy Laboratory of the US Department of Energy, said that there are ways to combat this problem.

Bat protection technology includes ultrasonic deterrents that can prevent bats from approaching wind turbines. Another option is to turn off the turbines at the end of summer and in the fall when bats migrate.

The study was published in Ecology and Evolution.