OLFACTION AND PREDATOR DETECTION IN COLEONYX BREVIS (SQUAMATA, EUBLEPHARIDAE), WITH COMMENTS ON THE FUNCTIONAL-SIGNIFICANCE OF BUCCAL PULSING IN GECKOS

Squamate reptiles rely heavily on two nasal chemical senses in directi ng most of their behavior: nasal olfaction and vomeronasal function. F or most behaviors in most species, the vomeronasal system is the predo minant sense. It has been suggested, however, that geckos are unusual in the extent to which they rely on nasal olfaction rather than vomero nasal function. In this study, we use defensive tail display as a beha vioral bioassay to examine the context and relative use of olfaction v s. vomeronasal function in a eublepharid gecko, Coleonyx brevis. When presented with appropriate snake-predator skin chemicals in the absenc e of relevant visual stimuli, C. brevis exhibits a defensive tail disp lay that has been shown to be adaptive in defending against snake pred ators. We demonstrate that olfactory cues alone are sufficient to prov oke the behavior and that geckos precede the display in many cases wit h ''buccal pulsing,'' a behavior that we suggest is an olfactory sampl ing mechanism analogous to mammalian sniffing. Our results support the gecko-olfaction hypothesis and demonstrate that geckos use nasal olfa ction to discriminate among potential predator species. We discuss alt ernative hypotheses for the origin of species-specific, chemosensory p redator identification in Coleonyx. (C) 1996 Wiley-Liss, Inc.