Precipitation patterns drive seasonal and spatial variation in behavior and physiology within an arid-adapted snake genus, Crotalus.

Abstract

Regardless of environmental conditions, organisms must maintain thermal and hydration states within tolerable limits, which can be especially challenging in arid environments. To mitigate environmental impacts, organisms may use behavioral and physiological alterations to buffer their internal states. Unfortunately, the degree to which behavioral and physiological responses contribute to tolerance of more arid conditions and the extent that organisms may tolerate increasing aridity remains unclear. Therefore, we simultaneously measured physiological and behavioral responses of Sonoran Desert rattlesnakes to seasonal and populational differences in aridity. We found that changes in evaporative water loss, osmolality, and activity across seasons and between sites appear to be driven by precipitation patterns. Earlier, more frequent, and greater amounts of rainfall between field sites resulted in differences in physiology and behavior within a single species. In contrast, two sympatric species showed similar seasonal physiological and behavioral patterns. Overall, our study demonstrates the importance of precipitation as a driver of activity and evaporative water loss and lends insight into the tolerance mechanisms that enable species to inhabit arid environments. Such information is critical as we attempt to predict impacts of climate change where most models forecast increased temperatures and decreased rainfall for many areas around the globe.