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Hibernators adjust the expression of torpor behaviourally and physiologically to balance the benefits of energy conservation in hibernation against the physiological and ecological costs. Small fat-storing species, like many cave-hibernating bats, have long been thought to be highly constrained in their expression of hibernation because they must survive winter relying only on endogenous energy stores. We evaluated behavioural microclimate selection in tri-colored bats (Perimyotis subflavus (F. Cuvier, 1832)) across a 3-month hibernation experiment under laboratory conditions. We also opportunistically tested for evidence of acclimatization in torpid metabolic rate (TMR). When given access to gradients in microclimate, bats tended to choose the warmest temperature available (11 [degrees]C) while almost completely avoiding the driest condition available (85% relative humidity at 8 [degrees]C). Furthermore, bats held at different temperatures over the course of the hibernation showed no differences in TMR when measured under common conditions at the end of hibernation. Taken together, our results suggest that selective pressures to conserve energy during hibernation are not overwhelmingly strong and further support the proposition that optimal expression of hibernation is something less than the maximal expression of hibernation unless the animal is nearing starvation. Key words: microclimate, optimal hibernation, Perimyotis subflavus, torpor, tri-colored bats. Les especes qui hibernent modulent l'expression de la torpeur de maniere comportementale et physiologique pour etablir un equilibre entre les avantages de la conservation d'energie durant l'hibernation et les couts physiologiques et ecologiques. II a longtemps ete considere que l'expression de l'hibernation chez les petites especes qui emmagasinent des graisses, telles que de nombreuses chauves-souris hibernant dans des cavernes, est restreinte puisque ces especes ne disposent que de reserves energetiques endogenes pour survivre a l'hiver. Nous avons evalue la selection comportementale du microclimat chez les pipistrelles de l'Est (Perimyotis subflavus (F. Cuvier, 1832)) au cours d'une experience durant laquelle elles etaient plongees dans une hibernation de 3 mois dans des conditions de laboratoire. Nous avons egalement verifie de maniere opportuniste la presence d'indices d'acclimatation reveles par leur taux metabolique en etat de torpeur (TMR). Lorsqu'un environnement presentant des gradients de microclimat leur etait accessible, les pipistrelles avaient tendance a choisir la temperature disponible la plus elevee (11 [degrees]C), tout en evitant presque completement la condition la plus seche (85 % d'humidite relative a 8 [degrees]C). En outre, les pipistrelles maintenues a differentes temperatures au cours de l'hibernation ne presentaient aucune difference entre elles quant a leur TMR, qui etaient tous mesures dans les memes conditions a la fin de l'hibernation. Mis ensemble, nos resultats suggerent que les pressions de selection axees sur la conservation d'energie durant l'hibernation ne sont pas dominantes, et appuient le postulat selon lequel l'expression optimale de l'hibernation est moindre que l'expression maximale de l'hibernation, a moins que l'animal soit dans un etat de sous-alimentation avancee. [Traduit par la Redaction] Mots-cles: microclimat, hibernation optimale, Perimyotis subflavus, torpeur, pipistrelles de l'Est., Introduction Hibernation was long thought to be almost exclusively motivated by an overarching need to save energy (and sometimes water) during seasonal periods of low energy availability. This idea led [...]

In multihost disease systems, differences in mortality between species may reflect variation in host physiology, morphology, and behavior. In systems where the pathogen can persist in the environment, microclimate conditions, and the adaptation of the host to these conditions, may also impact mortality. White‐nose syndrome (WNS) is an emerging disease of hibernating bats caused by an environmentally persistent fungus, Pseudogymnoascus destructans. We assessed the effects of body mass, torpid metabolic rate, evaporative water loss, and hibernaculum temperature and water vapor deficit on predicted overwinter survival of bats infected by P. destructans. We used a hibernation energetics model in an individual‐based model framework to predict the probability of survival of nine bat species at eight sampling sites across North America. The model predicts time until fat exhaustion as a function of species‐specific host characteristics, hibernaculum microclimate, and fungal growth. We fit a linear model to determine relationships with each variable and predicted survival and semipartial correlation coefficients to determine the major drivers in variation in bat survival. We found host body mass and hibernaculum water vapor deficit explained over half of the variation in survival with WNS across species. As previous work on the interplay between host and pathogen physiology and the environment has focused on species with narrow microclimate preferences, our view on this relationship is limited. Our results highlight some key predictors of interspecific survival among western bat species and provide a framework to assess impacts of WNS as the fungus continues to spread into western North America. [ABSTRACT FROM AUTHOR]