Ferrall, E.A., S. Perea, K.M. Morris, P.E. Pattavina, B.J. Irwin, J. Hepinstall-Cymerman, and S.B. Castleberry. (in review). Disparities in body mass of Perimyotis subflavus between cave and culvert winter roost sites in Georgia, USA. Ecology and Evolution.
Abstract
The tricolored bat (Perimyotis subflavus), once a common species in the eastern United States prior to the arrival of white-nose syndrome (WNS) to North America, has experienced significant disease-related mortality throughout much of its global range where it predominately hibernates in caves and mines. In coastal regions of the southeastern U.S., where there is a scarcity of caves and mines, tricolored bats often utilize road culverts as hibernacula. Previous research demonstrated that bats with higher body mass at the onset of hibernation have a higher probability of surviving repeated arousal events from WNS. Therefore, our objectives were to investigate the prevalence of Pseudogymnoascus destructans (Pd) in culverts, evaluate tricolored bat winter body mass metrics by roost type, and identify culvert characteristics that may be drivers of varying body mass throughout hibernation. From 2018-2022, we measured the 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 Pd over multiple years, culminating in the first confirmed case of WNS incidence in a Georgia culvert in 2022. Tricolored bats of both sexes utilizing caves weighed more in early hibernation than those in culverts, and in late hibernation those in culverts weighed greater than those in caves. Across all sites, we observed intersexual differences in both early and late hibernation mass, with female tricolored bats entering and leaving hibernation heavier than males. Despite having greater late-hibernation body mass, females experienced higher proportion of mass loss during hibernation, potentially due to differences by sex in torpor-arousal patterns and WNS infection rates. Furthermore, we observed that tricolored bats lost more mass as culvert length increased, suggesting a potential link between habitat characteristics and hibernation physiology. Overall, our results highlight the importance of sex in late-hibernation body mass dynamics and the combined influence of sex and culvert length on mass loss during winter hibernation. Investigating characteristics in culvert structures that impact bat body mass can aid our understanding of winter physiology in these hibernacula and ultimately aid in more targeted management strategies to mitigate WNS impacts. Additionally, understanding risk variables unique to individual tricolored bat colonies can guide managers on where to focus winter WNS monitoring efforts and potential treatments.