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Summary of Proposal LAN2940

TitleMicro-habitat usage under different predation risk pressures in natural populations of snowshoe hare.
Investigator Boudreau, Melanie - Trent University, Environmental and Life Sciecnes
Team Member
Dr. Murray, Dennis - Trent University, Environmental and Life Sciecnes
SummaryPredator-prey interactions have always been viewed as a key component in shaping ecological communities. Traditionally, ecologists viewed predation only as a direct interaction whereby prey are killed and consumed by predators, but recently ecologists have recognized non-consumptive effects of predation risk on developmental, physiological, or behavioral changes in prey. Investment into anti-predator tactics may come at the cost of survival, growth and reproduction. In theory, such non-consumptive effects can have as much of an impact as direct consumption, but to date long-term population-level implications of such effects are poorly understood. In the boreal forest, snowshoe hare populations undergo a regular cyclic fluctuation with 8-10 years between peak densities,with predator populations following this fluctuation with a lag of 1-2 years. During the hare population decline, predators can cause up to 100% of hare deaths, with lynx and coyote being the most important predators.However, recent work suggests that hare population declines involve non-consumptive predation effects as well, with hares during decline years experiencing chronic stress potentially leading to increased vigilance, altered foraging, and lower productivity. However, to date, perceived predation risk in snowshoe hares has been assessed only in penned hares leaving fundamental gaps in our understanding of: 1) how free-ranging hares respond to perceived risk, 2) whether risk responses transcend multiple (i.e., behavioral, physiological) axes, and 3) whether risk-related responses translate to demographic responses that are expressed at the population level. In the Kluane Lake region, hare populations have been monitored for over 30 years. Populations used in this study will be just out of their cyclic low and number of hares will be on the rise. To better understand the indirect effects of predation, risk will be manipulated by periodically running a domestic dog (a model for coyotes) through known home ranges of radio-collared hares, and responses will be compared to those of controls (experiencing normal risk). Stress levels, hare activity and habitat usage, energy expenditure and body mass changes will be monitored. Because the above changes can translate to fitness variability, survival and pregnancy rates will also be documented. We know that hares exhibit a spatial behavioral response to risk as seen in a higher use of cover. However, our study will be the first to try to objectively quantify habitat availability vs. habitat used under the different risk scenarios. We aim to use the spatial imagery provided to aid us in quantifying this variable by calculating the amount of available cover in known home ranges to the amount used by each individual. We can do this by overlaying GPS co-ordinates of hares onto the detailed spatial imagery provided. As the GPS data is accurate to a scale of 2m or less we wish that the spatial imagery data provided beat the same scale (2m) - if not finer (less than that) and we believe that TerraSAR-X imagery will suit our needs. Other ecological studies have used radar imagery to quantify canopy cover (e.g., de Knegt et al. 2010; review in Kasisckhke, Melack and Dobson 1997). Manipulations run from May-September and will be conducted both this year (2015) and again in 2016. Ideally we would have images corresponding with late spring (May) height of summer (July) and early fall (September) in order to truly represent changes in cover over the course of the manipulation each year as usage may vary with leaf cover.However, if this is not available we would at minimum require spatial imagery during the height of the growing season (July) which would at least give us the peak point in available browse and cover and we can document changes to that with metrics taken on site. Funding for this study is provided by the Natural Sciences and Research Council (NSERC).

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