Abstracts

Abstract: Heat stress is a common threat to the homeostasis of endotherms. Behavioral adaptations to alleviate heat stress, like seeking shade, wind, or altering activity patterns, are often less costly than physiological changes but may cause competition for thermal cover. Need for thermal cover may differ by sex, age class, or physiological status. For instance, peak lactation in most species of large mammals typically occurs during the hottest months. Thus, females are forced to forage and process foods during the heat to meet their nutritional requirements. The goals of this study are to evaluate behavioral adaptations of white-tailed deer (Odocoileus virginianus) to heat stress and assess competition for thermal cover with cattle (Bos spp.). We will deploy 40 GPS collars (30 deer, 10 cows) equipped with black-globe thermometers across the East Foundation's El Sauz Ranch in South Texas. Collars will record location and operative temperature at 30-minute intervals. We will also deploy black-globe thermometers across the landscape to monitor fluctuations of operative temperature with variation in herbaceous and woody cover and orientation relative to wind. Temperature and GPS data will be analyzed using resource selection functions and remote sensing will be used to identify important habitat characteristics. Knowledge of deer movements, resource selection, and competition for thermal cover will further our understanding of how heat affects deer and cattle and what landscape features mitigate this stress. The results of this study will enable managers to design habitat management regimes that may assist in mitigating the effects of heat stress on deer.