Geographic Differences in Behavioral Responses of Hatchling Lizards (Eumeces okadae) to Snake-predator Chemicals

Antipredator and tongue flicking responses of hatchlings of Eumeces okadae were compared between Kozu-shima Island, where they co-occur with snake predators, and Hachijo-kojima, a snake-free island. In Experiment 1 lizards from both islands showed higher tongue flick rates to cotton swabs bearing snake and prey chemicals than to controls. Lizards from Hachijo-kojima emitted more tongue flicks to snake chemicals than those from Kozu-shima. In Experiment 2 lizards from Hachijokojima showed higher tongue flick rates to cotton swabs bearing non-saurophagous, allopatric snake chemicals than to control stimuli. Lizards from Kozu-shima exhibited tail wave display, which may deflect attacks to the autotomous tail, more frequently to saurophagous snake chemicals than to non-saurophagous snake and control stimuli, but there were no significant differences in tongue flick rates among the three chemicals for these lizards. In Experiment 3 lizards were introduced into an unfamiliar terrarium treated with snake chemicals. Lizards from Hachijo-kojima emitted more tongue flicks in cages chemically labelled by snakes than in control cages. No significant differences were observed in tongue flick rates between snake labelled and control cages in Kozu-shima lizards, and their tongue flick rates in snake labelled cages were significantly lower than those of Hachijo-kojima lizards. There were no differences in the frequency of tail waves, wall-climbing, movements, or immobility between snake labelled and control cages in lizards from both islands. Based on the higher tail wave frequency and lower tongue flick rates in Kozu-shima lizards than in Hachijo-kojima lizards, we hypothesize that lizards from Kozu-shima have evolved the ability to recognize chemical cues from snake predators after a few tongue flicks and that the higher tongue flick rates by lizards from Hachijo-kojima indicate less efficient recognition or lack of recognition of predator chemicals.