You can’t see me: Background matching in the Western diamond-backed rattlesnake (Crotalus atrox)

Abstract

Abstract Coloration is crucial for ambush mesopredators’ survival as they depend on it for camouflage to hunt and avoid predation. Furthermore, coloration is especially important in ectotherms as it is linked to two essential functions for survival: thermoregulation and crypsis. In a context of trade-offs between thermoregulation and crypsis, the comprehension of how ectotherms employ color to address conflicting demands of thermoregulation and crypsis is limited. This study investigated background matching and thermoregulation in western-diamond-backed rattlesnakes (Crotalus atrox). Rattlesnakes were predicted to better match selected microhabitats in terms of color, luminance, and pattern than random microhabitats within their home range, and temperature was predicted to influence their body coloration. Pictures of fourteen radiotracked western diamond-backed rattlesnakes were taken in situ with a full spectrum camera (UV/VIS) and body temperature was recovered from internal temperature-datalogging radio-transmitters. Crotalus atrox matched the color, luminance, and pattern of the background better than a randomly selected background, thus enhancing crypsis. Additionally, rattlesnake coloration varied independently of temperature indicating that rattlesnakes are behaviorally modifying crypsis regardless of thermoregulation.