Responses to Animal and Plant Chemicals by Several Iguanian Insectivores and the Tuatara, Sphenodon punctatus

Abstract

We conducted experimental tests of the responses to food chemicals presented on cotton swabs or ceramic tiles by tuataras and insectivorous species from several families of iguanian lizards. Tu- ataras, which are primarily carnivorous, never tongue flicked but frequently bit cotton balls bearing prey surface chemicals, suggesting that they may be able to detect airborne prey chemicals via olfaction. None of the lizards tested, the agamids Chamaeleo pardalis and Acanthosaura crucigera, the polychrotids Anolis smallwoodi and Chamaeleolis chamaeleonides, the phrynosomatids Sceloporus variabilis and Uta stansburi- ana, and the crotaphytid Crotaphytus collaris, exhibited any differential responses among prey chemicals, chemicals from palatable plants, and pungency control or odorless control stimuli. The findings buttress previous work that has shown a lack of prey chemical discrimination in ambush foragers, including all sampled iguanian insectivores. Given that all tested omnivores and herbivores respond strongly to plant chemicals, they are also consistent with the hypothesis that discriminatory lingual and biting responses to plant chemicals occur only in species having diets with a large plant component. Correlated evolution between herbivory and plant chemical discrimination remains to be established. For unknown reasons, Sceloporus variabilis tongue flicked less frequently in tile tests with romaine lettuce stimuli than with cricket and banana stimuli.