Movement and spatial consumer-resource dynamics in a rapidly changing world

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The past 2 decades has witnessed enormous advances in our understanding of the multitude of factors influencing animal movement processes. Less attention has been devoted to the impact of climate change and anthropogenic landscape disturbance on spatial dynamics and population viability. My long-term objectives are to identify causal mechanistic links for herbivore migration, determine how movement contributes to local co-variation in the abundance of consumers and their resources, model the impact of spatial processes on consumer-resource dynamics, and use those simulation models to evaluate the impact of climate change and anthropogenic disturbance on the viability of migratory herbivores. I propose to address these objective using a mix of theoretical and field techniques in three well-studied ecosystems populated by migratory herbivore populations: (1) wildebeest and Thomson's gazelles in the open plains and wooded grasslands of Serengeti National Park, (2) wild and domesticated reindeer in the montane regions of Scandinavia, and (3) migratory woodland caribou in the boreal forests of northern Ontario. Field studies will be restricted to just the African and Scandinavian sites, since the relevant field measurements have already been obtained for woodland caribou. Theoretical modeling will be fully integrated into all 3 ecosystems, with spatially-explicit simulation models used to explore the implications of movement and spatial dynamics for ecological interactions. Predation risk will be assessed by mapping the utilization distribution of predators across the landscape, weighted by local variation in herbivore abundance since risk is generally inversely related to local prey abundance in most predator functional responses. Energetic benefits will be assessed by estimating herbivore diet either by direct observation or from animal-borne video cameras attached to radio-collars, combined with standard lab assays of digestible energy from proximate analysis. Energetic costs will be assessed by accelerometers routinely incorporated into GPS radio-collars, calibrated against behavioral observations. Spatially-explicit agent-based simulations will be used to evaluate the impact of observed movement trajectories, by integrating risk, energetic gain, and energetic costs over the entire annual migratory cycle. The observed movement trajectories for all 4 species will be modeled using multiphasic state-space models to estimate combinations of turn rates, directional bias, and step lengths conditioned on local landscape features, seasonality, and motivational state. The resulting movement models will be incorporated into spatially-explicit agent-based simulation models to evaluate long-term trends for population productivity and long-term- viability in relation to realistic levels of environmental stochasticity.