Travis Rusch

Stress Response from Male-Male Competition in Varying Thermal Environments

Environmental temperature influences virtually all aspects of organismal performance, including fitness. And since temperature varies throughout space and time, organisms must regularly compete for optimal thermal habitats, much as they do for other resources (e.g. territory, food, or females). However, competition for thermal resources imposes costs, often in the form of a stress response (i.e. increased corticosterone production). Elevated corticosterone promotes physiological and behavioral responses that can increase an organism’s chance of survival, but if left in an organism’s system for too long, it will reduce immunity, degenerate neurons, and lower fitness. Previous theoretical and empirical work indicates that, all else being equal, patchy thermal landscapes reduce the energetic cost of thermoregulation. Therefore, I hypothesize that lizards exposed to patchy distributions of preferred temperatures will have less stress (and thus lower levels of corticosterone) than those exposed to clumped distributions. Furthermore, patchily distributed resources are more difficult for territorial males to monopolize, and thus, subordinate males in patchy thermal landscapes should experience less stress than subordinate males in clumped thermal landscapes.