Prey chemical discrimination indicated by tongue-flicking in the eublepharid geckoColeonyx variegatus

Previous empirical studies of chemical discriminations by eublepharid geckos suggest that olfaction can mediate detection and appropriate response to prey and predator chemical cues. These discriminations can be made based on airborne cues without the necessity of tongue-flicking, the major means of chemical sampling for vomerolfaction, the sense mediated by the vomeronasal organs. Comparative histological and gross anatomical studies show that olfaction is most highly developed among squamates in the geckos, but that vomerolfaction is also well developed. In this study I conducted an experiment demonstrating that Coleonyx variegatus tongue-flicks and attacks at higher rates in response to prey chemicals than to a pungency control and odorless control. These results differ from those of a study in another laboratory of the same species because of differences in stimulus preparation and criteria for inclusion of data, but the results do not contradict the previous findings. It is hypothesized that eublepharids use both olfaction and vomerolfaction in appropriate circumstances to make adaptively important chemosensory discriminations. Experimental selective blocking of senses is needed to demonstrate conclusively the separate sensory roles. J. Exp. Zool. 281:21–25, 1998.