Ecophysiology of boreal small mammals: physiological variation and environmental change

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All organisms must balance energy intake against output on some timescale to survive and reproduce. Therefore, factors affecting energy balance will exert strong influence on evolution and, indeed, all ecological processes. The long-term goal of my program is to understand variation in mechanisms used by small, free-living mammals to maintain energy balance in the face of environmental change. This is important for understanding the evolution of physiological traits, and predicting consequences of climate change for wildlife and ecosystems. In the short-term, my group will focus on variability in two related sets of mechanisms: a) traits associated with whole-animal energy expenditure, such as metabolic rate and thermoregulation; and b) activity of the so-called "stress axis", which helps mediate predictable seasonal changes in energy use, and responses to acute environmental stressors (such as predation risk) via stress hormones. We will test hypotheses about responses of these traits to environmental change in long-lived mammals with low reproductive rates (bats, Chiroptera) vs. short-lived species with high reproductive rates (shrews, Soricidae) to assess the influence of life history on physiological variation. Theory predicts that long-lived species should be more flexible in response to environmental change because of selection pressure favouring adaptation to the broad range of conditions experienced during their lives. Individuals of short-lived species should be less flexible but these species may be subject to more rapid evolutionary change because of shorter generation times. We will study whole-animal metabolism by measuring rates of O2 consumption, CO2 production and body temperature in wild-captured animals, and stress axis activity by assaying stress hormones in blood or feces. Over the long-term we will test the hypothesis that inter-annual variation in these traits, within populations of bats and shrews, is correlated with both direct and indirect effects of climate change.