Additional Evidence for Barotrauma as a Cause of Bat Mortality at Wind Farms

The discovery of extensive bat mortality at wind farms has puzzled biologists, especially since many carcasses found under turbines exhibit no obvious injuries. A recent study proposed barotrauma – damage to body tissues caused by changes in pressure – as a possible explanation. We tested this hypothesis by examining 146 carcasses of hoary bats (Lasiurus cinereus), eastern red bats (Lasiurus borealis), and silver-haired bats (Lasionycteris noctivagans) collected during mortality surveys at a wind farm in eastern Pennsylvania. All carcasses were examined for both external and internal injuries. To assess barotrauma, we looked for blood in the nose and mouth, hemorrhaging in the lungs, and pooled blood in the thoracic and abdominal cavities. Of 146 carcasses examined internally, 54 (37%) had signs of barotrauma but no external injuries, 48 (33%) had external injuries but no signs of barotrauma, and 44 (30%) had both signs of barotrauma and considerable external injuries. A chi-square test found no association between the age or sex of bats and the incidence of barotrauma. These results support barotrauma as a contributing cause of bat mortality at wind farms.