No drought about it: Effects of supplemental hydration on the ecology, behavior, and physiology of free-ranging rattlesnakes

Hydration is a critical element for many physiological processes in vertebrates. While it seems intuitive that drought is stressful to animals, studies examining drought are typically observational and do not explicitly assess how the hydration state of study subjects influences their physiology and behavior. We examined how hydration affects several physiological and behavioral variables in free-ranging Northern Pacific rattlesnakes (Crotalus oreganus oreganus) by experimentally manipulating their hydration levels in the field. Our results suggest that supplemental water has a significant effect on reproduction, as all hydrated females gave birth during the experiment, while no control females did. We saw no effect of hydration on movement parameters; males moved a larger total distance and had larger home ranges than females, regardless of hydration status. Interestingly, body condition at the end of the study was significantly higher in hydrated snakes, suggesting that hydrated individuals might have been acquiring more food than control snakes. We saw no effect on baseline stress hormone concentrations or their increase in response to an acute stressor. Additional experimental studies are needed to better understand the pivotal roles of hydration in the physiology and behavior of reptiles.