Bat mortality is increased near moving, but not static, turbine blades at wind farms (WFs).2,9,14,21,23,25 The 2 leading hypotheses for the mortality include blunt force trauma from being struck by moving turbine blades and barotrauma. Barotrauma is a phenomenon in which abrupt air pressure changes cause tissue damage to air-containing structures (eg, lungs). It is suggested by some to cause a high proportion of bat deaths at WFs, with up to 90% of bats reported to have lung lesions consistent with barotrauma.4 Key diagnostic features of pulmonary barotrauma include microscopic detection of hemorrhage and edema in airspaces with vascular congestion and interstitial bullae.1,4,15,29 However, pulmonary barotrauma diagnosis has primarily been based on examination of lung tissues from salvaged bat carcasses. The time from death to carcass collection (and eventual tissue fixation) in these cases is not typically known, and in some cases only an estimated window of time (eg, died the previous night) is at best available.3,4 Prior to collection, the carcasses may be exposed to various environmental conditions (eg, temperature, sunlight) that can alter tissue decomposition kinetics and tissue morphology.35,42 Additionally, biologists frequently salvage bat carcasses from WFs for study and may freeze them for long-term storage, which could cause additional morphologic changes.
We designed a 2-part forensic investigation into the etiology of bat mortality at WFs. First, we hypothesized that postmortem decomposition and environmental conditions would influence the development of morphologic artifacts in the lung that could mimic and confound the diagnosis of pulmonary barotrauma. We examined a laboratory mouse model to longitudinally study the appearance of these morphologic parameters to determine the diagnostic utility of salvaged lung tissue for barotrauma diagnosis. Second, we designed a controlled experiment to evaluate bat carcasses for signs of traumatic injury and barotrauma. To this end, we examined salvaged bats collected from a central Illinois WF compared with a control group collected from downtown Chicago that had died following collision with a building.