Understanding the role of infectious diseases in shaping animal populations is essential for conserving ecosystems, particularly as increased anthropogenic movement supports new pathogen invasions. Heterogeneities in infection among individuals in a host population can influence transmission and ultimately drive host population responses to virulent diseases. Differences in infection between sexes are often overlooked but are an important source of inter-individual heterogeneity that can influence pathogen transmission. To explore sex-biases in pathogen transmission, infection severity, and disease impacts, we used data from a multi-host fungal pathogen Pseudogymnoascus destructans (Pd), the causative agent of white-nose syndrome in bats, collected from six species of bats at 43 sites across the northeast and midwestern U.S. We hypothesized that Pd infection would be higher in male bats given their promiscuous mating behavior during the fall exposure period and likely lower immune investment, as has been demonstrated in other species.
Results/Conclusions
Contrary to our hypothesis, we found that females were consistently more likely to be infected and suffered from higher fungal burdens than male conspecifics when there was a clear sex-bias. Furthermore, we found female bats were less likely than males to survive their infections. Previous research has suggested that female bats have shorter and cooler torpor arousal bouts, which may help conserve energy for spring reproduction. This unique torpor expression by females could limit opportunities for females to inhibit fungal growth through euthermia. Although male bats likely have more frequent contacts during mating, our results suggest that differences in torpor ecology are likely more important than sex-based differences in contacts. More broadly, higher impacts in females are likely to have cascading effects on populations and extend the consequences of disease beyond the periods when transmission is highest, by limiting recruitment and increasing the risk of Allee effects.