Sensory basis of navigation in snakes: the relative importance of eyes and pit organs

Abstract

Animal movements govern most ecological interactions, from predation to reproduction and survival. How animals move through the environment depends on available sensory information. Some snakes are able to perceive infrared (IR) radiation in addition to visible light. Research on this sensory system has been almost exclusively focused on predation, and researchers have largely found that vision and IR compensate for each other when one or the other is absent. However, IR sensing likely has much broader functions, including navigation in the environment. Many features in the environment of pit vipers are both visually and thermally salient and could be used for orientation. Here, we tested how vision and IR sensing interact in sidewinder rattlesnakes, Crotalus cerastes, in a simple navigation task in the field. Unlike in a predatory context, IR sensing did not compensate for the lack of vision. Snake movement paths were more tortuous, and snakes were less likely to encounter landmarks when eyes where occluded but were unaffected when pit organs were occluded. These findings suggest that the interaction between visual and IR cues may depend on context, and have important implications for our understanding of the evolution of IR sensing.