Alberta wind turbines kill bats via internal pressure drop, study finds

August 23, 2026 at 06:50 AM1 min

This digest was compiled by AI from multiple sources — links to the originals are below.

University of Calgary biologists found that 69 of 75 necropsied bats from an Alberta wind farm died from internal hemorrhaging caused by sudden air pressure drops near turbine blades, not collisions. The 2008 study in Current Biology identified barotrauma as the cause of death for bats that showed no external injuries. The finding explains why bats, despite echolocation, are vulnerable to wind turbines during migration.

Key Facts

Of 188 bats collected under turbines at an Alberta wind farm, 87 had no external injuries.
Necropsies of 75 fresh carcasses revealed internal hemorrhaging in 69 bats, or 92%.
All 17 bats examined histologically showed pulmonary lesions.
The study was published in Current Biology in 2008 by a University of Calgary team led by Erin Baerwald.
Researchers calculated pressure drops of 5 to 10 kilopascals in the blade wake, a range lethal to small mammals.

The Necropsy Findings

A University of Calgary team led by Erin Baerwald collected 188 bats killed overnight at a wind farm in southwestern Alberta, a major migration route. Of those, 87 bats had no external injury that could explain their death. The team necropsied 75 of the freshest carcasses in the field and found that 69 had hemorrhaging inside the chest or abdomen. Histological examination of 17 bats showed pulmonary lesions in every case.

Barotrauma Mechanism

The cause of death was identified as barotrauma, tissue damage from sudden pressure change. Wind turbine blades create zones of sharply lower pressure behind them, calculated at 5 to 10 kilopascals. A bat flying into this low-pressure pocket experiences rapid expansion of air in its lungs, tearing capillaries and causing fatal internal bleeding. Bats' lungs are large, elastic, and balloon-like, making them vulnerable to decompression, unlike birds' rigid lungs.