for National Geographic News
Wind turbines can kill bats without touching them by causing a bends-like condition due to rapidly dropping air pressure, new research suggests.
Scientists aren't sure why, but bats are attracted to the turbines, which often stand 300 feet (90 meters) high and sport 200-foot (60-meter) blades.
The mammals' curiosity can result in lethal blows by the rotors, which spin at a rate of about 160 miles (260 kilometers) per hour.
But scientist Erin Baerwald and colleagues report that only about half of the bat corpses they found near Alberta, Canada, turbine bases showed any physical evidence of being hit by a blade.
A surprising 90 percent showed signs of internal hemorrhaging—evidence of a drop in air pressure near the blades that causes fatal damage to the bats' lungs with a condition called barotrauma.
In humans, the condition is related to the bends and can affect divers and airplane passengers during ascents and descents.
(Related story: "Military Sonar May Give Whales the Bends, Study Says" [October 1, 2003])
"As a turbine blade goes around, it creates lift—like an airplane's wings—and there is a small zone of [dropping] pressure, maybe a meter or so in diameter, on the tips of the blades," explained Baerwald, a doctoral candidate at the University of Calgary, in Alberta.
"Bats fly through this area, and their lungs expand, and the fine capillaries around the edges of the lungs burst."
The bats' lungs subsequently fill with fluid, and the animals essentially drown.
"We compare it to divers—they are pretty much dying of the bends," Baerwald said.
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