Population ecology of arctic birds and mammals in a changing climate

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The role of trophic interactions in controlling animal populations remains controversial, especially in Arctic ecosystems. Yet, the rapid pace of climate warming in Polar regions has a strong potential to disrupt species interactions and affect their population dynamic, especially for cyclic populations or those exploited by humans such as hunted species. The aim of my research program is to improve our fundamental understanding of the population dynamic of arctic birds and mammals and to determine how factors controlling populations, especially trophic interactions, will change with climate warming. Over the next 5 years I will study (1) the role of predation in generating population cycles in the Arctic, (2) seasonality as a potential driving force of population cycles, (3) the interaction between snow and animal demography and (4) how environmental change can affect the balance between hunting and natural mortality in exploited species. First, I will test experimentally the hypothesis that predation can generate lemming population cycles through a combination of direct (mortality from predation) and indirect effects (maternal effects on reproduction mediated by stress hormones). This will be achieved by measuring lemming demography and physiology using a large-scale manipulation (predator exclusion over a large fenced plot). Second, I will examine whether the peculiar seasonality of lemming demography (high fecundity and low mortality in winter) may be a driver of population cycles by measuring the length of the winter breeding season and modelling the effect of winter breeding on population growth. Third, a collapse of lemming cycles has been reported in areas where the winter has warmed, possibly due to changing snow condition. I will study the links between meteorological conditions, snow physical properties and winter reproduction in order to develop a model that could predict annual lemming abundance based on conditions of the snow pack. Fourth, I will assess how the interaction between human exploitation and changing environmental conditions can affect the population dynamic of migratory birds. I will examine how trophic mismatch can switch the balance between cause-specific mortalities (hunting vs natural causes) in young snow geese using a long-term capture-mark-recapture study. A mismatch occurs when plant phenology respond more quickly to climate warming than herbivores, which negatively affects herbivore reproduction. This research program will provide training for 7 graduate and 10 undergraduate students. It will contribute to a paradigm shift where predation is emerging as a dominant force controlling animal populations in a wide range of ecosystems. By combining empirical and modelling studies, I will also provide tools to generate quantitative predictions on future changes in wildlife populations in response to a rapidly changing environment.