Disparities in Perimyotis subflavus Body Mass Between Cave and Culvert Hibernacula in Georgia, USA

The tricolored bat (Perimyotis subflavus), once common in the eastern United States, has experienced significant mortality due to white-nose syndrome (WNS), a fungal disease that primarily affects bats hibernating in caves and mines. In coastal regions of the southeastern United States, where caves and mines are scarce, tricolored bats often use roadway culverts as hibernacula. However, WNS infection dynamics in culverts are poorly understood. Previous research indicated that bats with higher body mass at the onset of hibernation have a higher probability of surviving repeated arousal events from WNS. Therefore, we compared tricolored bat winter body mass between cave and culvert hibernacula and identified culvert characteristics influencing body mass during hibernation in Georgia, USA. From 2018 to 2022, we measured body mass of 754 individuals in early and late hibernation across 32 culverts (n = 497) and four caves (n = 257). Our study revealed a southward spread of the fungus over multiple years, with the first confirmed case of WNS in a Georgia culvert in 2022. Overall, tricolored bats in caves weighed more in early hibernation than those in culverts, but bats in culverts weighed more in late hibernation. Across all sites, female tricolored bats entering and leaving hibernation had greater mass than males but lost more mass during hibernation, possibly due to differences in torpor-arousal patterns and WNS infection rates. Additionally, all bats lost more mass in longer culverts. Understanding culvert characteristics affecting bat body mass will inform management strategies to mitigate WNS effects. Identifying risk factors for specific tricolored bat hibernacula can guide managers on where to focus winter WNS monitoring efforts and potential treatments.