Collaborative Research: Strike while the snake is hot: will increasing nighttime temperatures make an endothermic keystone species more susceptible to ectothermic predators?

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The balance between predator and prey is a fundamental force shaping natural populations. Increasing global temperatures could have major indirect effects on ecosystems by disrupting the predator-prey relationships of keystone species. The potential for such an impact is greatest when one of the two is an ectotherm (such as a reptile) whose body largely conforms to the environmental temperature, and the other is an endotherm (such as a mammal) that maintains a fairly constant body temperature. Kangaroo rats are keystone species in North American deserts, and alterations in their foraging behavior and population ecology can cascade through the ecosystem. Rattlesnakes are major predators of kangaroo rats whose daily and seasonal activity and predatory performance is directly tied to the temperature of the environment. This proposal combines laboratory and field experiments that comprehensively document the details of the activity cycles, behaviors, and performance of rattlesnakes and kangaroo rats in relation to temperature. This information will then be used to develop computer simulation models of how temperature regulates equilibrium between predator and prey populations through changes in their interaction dynamics. These models will have broad conservation impacts by allowing researchers to quantify and actually predict complex indirect effects of climate change on natural ecosystems. This project will also have broad impacts on society by training several dozen undergraduate and graduate students from diverse backgrounds, and by inspiring high school students to pursue STEM careers through the implementation of training modules using high-speed video and biomechanics in schools that serve economically disadvantaged populations. Predation is a fundamental evolutionary force, shaping many aspects of behavior and morphology of predators and prey. Because of the centrality of predation in the lives of most organisms, predator-prey interactions can directly affect ecosystem structure and stability. However, the detailed mechanics of predator-prey interactions are rarely considered when ecologists examine the role of predation in structuring communities. Those details may be crucial in understanding how climate change will affect key species interactions. The objective of this project is to comprehensively evaluate the potential for increasing environmental temperature to disrupt predator-prey interactions in keystone species (rattlesnakes and kangaroo rats) across a naturally occurring thermal cline, and then use this data to parameterize and test computational models examining how temperature changes could alter predator-prey equilibria. Researchers will conduct a series of hierarchical experiments and analyses that will: (1) Use in vivo and in vitro laboratory analyses to quantify impacts of temperature on physiology and function of the musculoskeletal system used to power predatory strikes in snakes. (2) Combine laboratory and field experiments to examine the impact of temperature on whole-animal predatory performance. (3) Use detailed direct observation of kangaroo rats and rattlesnakes in nature at different latitudes to establish baseline relationships between temperature and physical performance, activity cycles, foraging behaviors, movement ecology, and population demographics. (4) Use agent-based computational simulations calibrated with observational and experimental data to predict focal population dynamics s across different thermal regimes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.