Shifting effects of host physiological condition following pathogen establishment

Understanding host persistence with emerging pathogens is essential for conserving populations. Hosts may initially survive pathogen invasions through pre-adaptive mechanisms. However, whether pre-adaptive traits are directionally selected to increase in frequency depends on the heritability and environmental dependence of the trait and the costs of trait maintenance. Body condition is likely an important pre-adaptive mechanism aiding in host survival, although it can be seasonally variable in wildlife hosts. We used data collected over seven years on bat body mass, infection, and survival to determine the role of host body condition during the invasion and establishment of the emerging disease, white-nose syndrome. We found that when the pathogen first invaded, bats with higher body mass were more likely to survive, but this effect dissipated following the initial epizootic. We also found that heavier bats lost more weight over winter, but fat loss depended on infection severity. Lastl..., We studied the arrival and establishment of P. destructans at 24 hibernacula (caves and mines where bats spend the winter) in Virginia, Wisconsin, Illinois, and Michigan over seven years (Tables S1–S3). We visited sites twice per winter and collected data on infection status and body mass of bats. At each site, we sampled individual bats (Table S1, mean = 9.2, range: 1–50) stratified across site sections. Because sites used in this study were primarily small mines where it was possible to observe all bats present, in many instances, all individuals in the population were sampled. For each bat, we collected a standardized epidermal swab sample (Langwig et al. 2015 Proceedings B), attached a unique aluminum band, and measured body mass using a digital scale (GDealer, accuracy +/- 0.03 grams). Because common condition indices are no more effective than body mass for estimating fat stores, we did not include information on bat forearm size in order to reduce handling disturbance. At every v..., No special programs are required to open the data files.Â