All species are susceptible to death by sudden change in air pressure, Baerwald said. "But the larger the animal is, the bigger the air pressure drop has to be. We know that four kilopascals [a unit of pressure] is enough to kill a rat. Bats are much smaller. We found that these wind turbines produce a five to 10 kilopascal drop." Birds are less vulnerable to the drop, because they have rigid, tubular lungs, compared to the balloon-like structures of bat lungs, which are much like human lungs. "It's one of those things we have speculated on for a long time," conservation scientist Edward Arnett of Bat Conservation International in Austin, Texas, told Discovery News. "It's an important finding on the cause of the fatalities. They're not offered much room for error. If they avoid being struck at the last minute, they still may be killed by this rapid change in air pressure." However, he added, "It may not lead us directly to any solution. Whether they're getting struck or they're dying from the barotrauma may or may not make any difference. We have to find ways to keep them away from the turbines." "There are a lot of people testing different forms of mitigation," Baerwald said. "Right now the most promising one is to shut turbines down during slow wind speeds during the fall migration at night." These are the conditions when bats are most active. Tests of this approach at her site in Alberta and elsewhere are promising, she said. Related Links: Jessica Marshall's blog: EnvironMental Case Bat Conservation International |
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