Cooperative Fish and Wildlife Research Units Program: Virginia
Education, Research and Technical Assistance for Managing Our Natural Resources

Since its February 2009 detection in Virginia hibernacula, the fungal pathogen Pseudogymnoascus destructans (P.d.) has had a marked impact on cave bats in the Commonwealth. From 2008-2013, we documented these impacts through fall swarm, early hibernation, and late hibernation surveys at 15 hibernacula in western Virginia. We coupled these surveys with biennial winter hibernacula counts in 2009, 2011, and 2013. To estimate percent declines in bat presence or relative activity, we used fall swarm capture per-unit-effort data, and the winter hibernacula absolute counts. To examine a metric that could serve as a proxy for health, we compared individual measures of body mass index (BMI) across years for fall swarm, early hibernation, and late hibernation/spring staging. We captured 4,524 bats of eight species, with species-specific capture success declining by 75-100% in some hibernacula since 2008. Little brown bats (Myotis lucifugus) were hardest-hit, by measure of winter hibernacula counts (AVG. = 99.0% decrease in counts), while tri-colored bats (Perimyotis subflavus; 89.5% decline) and Indiana bats (M. sodalis; 33.5% decline) also have been markedly impacted. Graphical analyses of captures-per-trap-hour in fall swarm showed some conservative patterns in decline for little brown bats, tri-colored bats, and northern long-eared bats (M. septentrionalis), but suggest a modest rebound for Indiana bats in recent years. Fall swarm trends in BMI suggested some drops in the metric post-presumed-P.d. exposure, but these trends did not hold across both sexes or across seasonal time blocks. Lower densities of little brown bats and individuals persisting in caves with P.d. for multiple years may suggest a competitive advantage for the few survivors. However, our inconclusive BMI metrics and little brown bat band recovery data do not support this theory. Lesser (but still apparent) declines in Indiana bat numbers mirrors trends seen elsewhere in the mid-Atlantic and the Northeast, and band recoveries suggest long-lived individuals persisting. Given that some sites were P.d.-positive for just one year by the conclusion of this study, we emphasize that continued surveys in this region are necessary to ascertain long-term effects in P.d. Additional surveys will determine if populations in these hibernacula will persist or face extirpation due to presumed low recruitment and survivorship.