Ecological energetics, behavioural variation and wildlife disease

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Infectious diseases of wildlife are an increasing concern as global travel and trade affect pathogen dispersal, and environmental change affects host susceptibility. There is growing realization that pathogens can cause species extinctions, loss of biodiversity and impacts on human public health and the economy. In North America, hibernating bats face an ongoing conservation crisis from the invasive fungal disease white-nose syndrome. The cold-loving WNS pathogen infects the skin of bats during hibernation causing a cascade of physiological changes that ultimately cause bats to expend their winter fat reserves too quickly. As for other pathogens that increase host energetic costs, traits that help bats increase energy intake or reduce expenditure could be crucial for survival. The WNS pathogen is spread by contact between bats but also from infected substrates in caves. Thus repeatable differences in sociability or explorative behaviours (i.e., personality), could affect the risk of pathogen exposure and influence survival. My long-term objective is to test the broad hypothesis that behavioural and physiological variation among individuals, social groups and populations of hosts affects host-pathogen dynamics and wildlife disease impacts. For this Discovery Grant, my short-term objectives are to use WNS in bats to test three hypotheses that emerge from my long-term goal: 1) Individuals with physiological traits that improve winter and summer energy balance (high food intake and fat storage, high expression of periodic reductions in body temperature and metabolism called torpor) will have higher annual survival after invasion resulting in a phenotypic shift toward these traits in persisting bat populations; 2) Individuals with behavioural traits that reduce risk of pathogen exposure (less sociable, explorative, smaller homerange) will have higher annual survival after invasion leading to population-level phenotypic shifts in behaviour; and 3) Environmental manipulations that improve both the intake and output sides of the energy budget can improve vital rates for pathogen-impacted populations. To address Objectives 1 and 2, my students and I will add to our large dataset on pre-WNS energetic and behavioural traits of marked bats in central Canada, with data from survivors that remain after WNS invasion. We will also compare summer homerange and torpor expression between a WNS-susceptible and WNS-resistant species. To address Objective 3 we will test the influence of habitat manipulations that could increase energy intake or reduce energy expenditure on survival and reproduction of bats with WNS. Despite potential impacts of wildlife pathogens, we have relatively few experimental data revealing how host population respond, and few tools to combat wildlife disease outbreaks when they occur. My program will shed light on the evolution of hosts in response to pathogens as well as potential management strategies to combat WNS and other diseases.