New study reveals link between complex migration patterns and risk of collision for North America's most vulnerable tree-roosting bats.
09.09.25
Austin, Texas (Sept 9, 2025) – Scientists from Bat Conservation International (BCI), the University of Florida (Gainsville), and the University of Maryland Center for Environmental Science Appalachian Laboratory, along with a group of collaborating scientists and conservation biologists, discovered that hoary bats (Lasiurus cinereus) and eastern red bats (Lasiurus borealis) may be at higher risk from wind energy facilities due to their unusual migration patterns. According to this group’s new study in Ecology Letters, these species migrate to both higher and lower latitudes in the autumn, indicating that they undertake long and wandering migrations. The large-scale effort referenced in the study links this migratory strategy (pell-mell migration) to the risk of a bat encountering a wind energy facility.
It is estimated that hundreds of thousands of North American bats die each year due to collisions with wind energy turbines, and three migratory tree-roosting bat species — hoary, eastern red, and silver haired bats (Lasionycteris noctivagans) — make up nearly 80% of these deaths. Compounding the problem is the rapidly increasing development of wind energy facilities as the world transitions to renewable energy sources.
“We’ve reached a critical point for the protection of these bat species,” says Dr. CJ Campbell, research scientist for Bat Conservation International and lead author of the study. “The relationship between bat migration and fatalities at wind facilities has been difficult to understand. This research reveals an unseen aspect of their migration patterns and moves us closer to understanding how to mitigate this conservation threat.”
Using a large-scale study focused on the three aforementioned bat species, the research team used chemical markers to track their migration. They analyzed stable isotope markers in bat fur to learn where and how the bats travel. This collaborative effort was the largest of its kind, analyzing thousands of fur samples and offering an unmatched level of detail into bat migration patterns.
“Understanding how animals move is essential for protecting them, especially when human structures like wind turbines are transforming the landscape, says study coauthor Dr. Hannah Vander Zanden, Assistant Professor and Director of the Archie Carr Center for Sea Turtle Research in the Department of Biology at the University of Florida. “This study has helped us understand the mystery of why certain bat species have been at greater risk of encountering wind turbines in the fall migration period. These bats aren’t just heading south for the winter – they’re taking the scenic route, and that detour could be deadly.”
The foundation of the stable isotope approach is based on techniques developed for human forensics. When bats are eating and drinking water, their fur (like human hair) reflects the stable isotopes of their environment, and when analyzed, can provide information about where the bat has been. Hydrogen is the most useful isotope in this case, as it varies due to local precipitation and can indicate the approximate latitude from which the bat traveled.
“We wanted to see if the bats being killed at wind turbines were doing anything differently,” says Dr. Campbell. “Our approach is a powerful but underutilized tool, and an excellent way to track bats that are too small or fly too far to be tagged. We kept getting the signal that individual bats were traveling north before making their way south for the winter months. This is very unusual behavior, and so unexpected that we spent years refining our approach and double-checking our data. After these efforts, we now provide evidence that the bat species that moving to higher latitudes first were more associated with wind energy facilities.”
The migratory motives of these bats remain unknown, but the authors suggest that they might be pursuing seasonal insect prey or mating opportunities.
Read the study in its entirety at https://onlinelibrary.wiley.com/doi/10.1111/ele.70202.
About Bat Conservation International
Bat Conservation International is a global conservation organization dedicated to ending bat extinctions. Our team works worldwide to conserve caves, restore critical habitats in danger, and ensure the survival of the world’s bat species. For more information, visit batcon.org.
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