Grant: Discovery Grants Program - Individual

My research program examines species interactions in food webs to understand the mechanisms by which interactions between predators and their prey are affected by alternative food sources or other predators. This understanding will enhance the ability to predict how species loss or environmental change will affect ecosystem structure and dynamics. In particular, the rapidly warming northern climate is relaxing distributional limits, creating novel interactions between expanding and endemic species. Arctic foxes are the main terrestrial predator throughout the Arctic; their primary year-round prey are lemmings, but they also feed extensively on migratory birds in summer and fall and consume seals on the sea ice in winter. They also impact other species by modifying the physical environment; by concentrating nutrients on dens, Arctic foxes enhance soil nutrients and increase plant productivity, which may attract lemmings and other herbivores. I am investigating interactions between Arctic foxes, their prey, and competitors near Churchill, Manitoba, on the west edge of Hudson Bay, where boreal forest transitions to Arctic tundra and the impact of climate change is likely to be large. Declines in sea ice are threatening polar bears, which provide terrestrial predators access to seal carrion. The recent incursion of red foxes onto the tundra is another threat to Arctic foxes, which are smaller and may alter their den use and foraging patterns, while the introduction of meadow voles alters resource availability to rodent predators. I will train 13 thesis students while addressing several short-term objectives. We will examine habitat use by Arctic foxes and red foxes breeding on the tundra using satellite telemetry to determine if red fox use of tundra dens affects Arctic foxes, and investigate the chronology of den occupancy by red foxes to determine if they usurp Arctic foxes. We will assess how varying prey availability affects diet breadth and overlap between these species using stable isotopes, as well as fox density and home ranges using non-invasive genetic sampling and spatial capture-recapture modelling. Using provincial harvest records we will assess fox population responses to changes in coastal resource availability, which may affect predation pressure on other prey, so we will also examine these indirect effects by comparing annual variation in prey populations. To assess the impacts of ecosystem engineering by foxes we will reconstruct lemming diets on fox dens and examine how fox dens promote shrub growth on upland tundra. Understanding the impacts of expanding southern species and indirect interactions among fox prey populations will help predict the wider consequences of climate change. Examining the importance of fox den sites for other organisms will reveal the broader impact of changes in fox populations at the southern edge of their distribution on Arctic biodiversity.