Lingually mediated discriminations among prey chemicals and control stimuli in cordyliform lizards: Presence in a Gerrhosaurid and absence in two cordylids

Insectivorous lizards that actively search for food, but not those that hun t by ambush, locate and identify pre, chemicals by tongue-flicking, which g athers chemical samples for sensory analysis. However, only a tiny fraction of lizard species has been studied. One assumption of the comparative stud ies is that presence or absence of prey chemical discrimination is stable w ithin most families because extensive data show that foraging mode is stabl e in most families. I present new experimental evidence on the relationship in cordyliform lizards, the families Cordylidae and Gerrhosauridae. The on ly previous data for the ambushing cordylids revealed no evidence of pre!: chemical discrimination in tests of Cordylus cordylus requiring lizards to tongue-flick cotton swabs held by an experimenter In additional tests on C. cordylus, we presented chemical stimuli on ceramic tiles placed on the cag e floors and observed responses through one-way glass. We conducted both sw at, tests and tile tests on the cordylid Platysaurus pungweensis. Neither c ordylid species exhibited any sign of prey chemical discrimination, showing that experimenter's presence does not explain the absence of discriminatio n in the swab tests and extending the absence of prey chemical discriminati on to another cordylid genus. Swab tests showed strong prey chemical discri mination in the actively foraging gerrhosaurid Gerrhosaurus validus, which tongue-flicked and bit swabs at higher rates in response to prey chemicals than to control stimuli. These findings are consistent with those for G. ni grolineatus and with the minimal foraging data available for Gerrhosauridae . All available data on cordyliform lizards support the relationship betwee n foraging mode and chemosensory behavior and agree with the assumption of intrafamilial stability of prey chemical discrimination. Additional data ne eded on cordyliform foraging and prey chemical discrimination are noted.