Scientists trying to figure why tens of thousands of bats are killed by wind turbines each year think they've figured out a key piece of the puzzle: The bats think the turbines are trees, reports Nature World News. Using thermal and infra-red surveillance cameras, researchers discovered that the bats deliberately flock to the turbines, perhaps confused by the wind currents generated by the devices and unable to tell the difference once they get near because of their lousy vision, says the study in the journal PNAS. Notably, the bats tend to stay away if turbine blades are moving at full speed, which likely means that the air turbulence warns them to stay away. But if the blades are turning more slowly—and if the bats have just enough moonlight to make out a tall thing that looks like a tree—the results are lethal.
"They don't have anything in their evolutionary history that would prepare them for something that looks and feels like a tree but isn't a tree," lead author Paul Cryan of the US Geological Survey tells Australia's ABC Science. So why would the bats be flying toward the tops of tall trees in the first place? Researchers assume it's because the bats would expect to find insects or another food source there, but it's only a guess because so little is known about bat behavior, explains the USGS. The next step, then, is to observe bats around treetops in the wild to see what's going on. "If we can understand why bats approach wind turbines, we may be able to turn them away," says Cryan. (A bat long thought to be extinct recently turned up.)