A snake of a different color: physiological color change in Arizona black rattlesnakes

Abstract

Coloration may serve a variety of behavioral (e.g., crypsis, communication) and physiological (e.g., thermoregulation, protection) functions for terrestrial ectotherms. However, optimal coloration for a given function may vary over environments (spatial or temporal) or conflict with other functions. Physiological color change (rapid change due to movement of pigment granules within chromatophores) may be an adaptation to resolve conflicting selective pressures on coloration. The proximate factors related to physiological color change are well known in many animals, but few studies have investigated the ecological or evolutionary implications of this behavior. Here, we present alternative hypotheses for physiological color change and discuss biotic and abiotic factors that may have led to the maintenance and/or loss of this behavior among populations of Arizona black rattlesnakes (Crotalus cerberus). We discuss what is known about this behavior and propose to investigate the function and evolution of coloration and color change in C. cerberus.