Chemosensory cues associated with snake predators affect locomotor activity and tongue flick rate in the whiptail lizard, Aspidoscelis dixoni Scudday 1973 (Squamata Teiidae)

Abstract

The unisexual teiid lizard Aspidoscelis dixoni Scudday 1973 is shown experimentally to be capable of detecting and responding to chemosensory stimuli from three species of naturally-occurring sympatric predatory snakes (Masticophis flagellum, M. taeniatus, Arizona elegans) and to discriminate these stimuli from those associated with a non-predatory snake (Leptotyphlops humilis segregus), as well as controls (water and cologne). Each lizard was exposed separately to the following: chemical stimuli from each of the predatory snakes, non-predatory, snake, water control, or pungency control (cologne). Lizards were placed in a test chamber whose floor was divided into 4 square grids of equal size, and for each trial, the number of times that a grid was crossed (locomotor activity), the number of tongue flicks observed (tongue flick rate, TFR), and time from beginning of trial to first tongue flick (latency), were recorded. Lizards crossed grid lines at significantly higher rates when exposed to chemosensory cues associated with all predatory snake species as compared to activity in the presence of nonpredator snake cues, water or cologne. There were no differences in number of grid crossings elicited by any of the three predatory snakes. TFR differed significantly among all treatments, but no significant difference was found among lizards exposed to water, cologne, or cues associated with L. h. segregus. TFRs were significantly higher, and latencies significantly lower, when lizards were exposed to chemosensory cues associated with predatory snake. Results suggest that because all lizards had no prior experience with any of the snakes, their ability to detect and respond to chemosensory cues of predators must be innate.