Olfaction and predator detection inColeonyx brevis (Squamata: Eublepharidae), with comments on the functional significance of buccal pulsing in geckos

Squamate reptiles rely heavily on two nasal chemical senses in directing most of their behavior: nasal olfaction and vomeronasal function. For most behaviors in most species, the vomeronasal system is the predominant sense. It has been suggested, however, that geckos are unusual in the extent to which they rely on nasal olfaction rather than vomeronasal function. In this study, we use defensive tail display as a behavioral bioassay to examine the context and relative use of olfaction vs. vomeronasal function in a eublepharid gecko, Coleonyx brevis. When presented with appropriate snake-predator skin chemicals in the absence of relevant visual stimuli, C. brevis exhibits a defensive tail display that has been shown to be adaptive in defending against snake predators. We demonstrate that olfactory cues alone are sufficient to provoke the behavior and that geckos precede the display in many cases with “buccal pulsing,” a behavior that we suggest is an olfactory sampling mechanism analogous to mammalian sniffing. Our results support the gecko-olfaction hypothesis and demonstrate that geckos use nasal olfaction to discriminate among potential predator species. We discuss alternative hypotheses for the origin of species-specific, chemosensory predator identification in Coleonyx.