Elevated tongue-flicking and biting by the insectivorous lygosomine skink Mabuya macularia to prey, but not plant, chemicals

Abstract

The ability of an insectivorous scincid lizard, Mabuya macularia to discriminate among prey chemicals and control substances and its responses to chemical cues from several plant species eaten by herbivorous and omnivorous lizards were examined experimentally using the swab method. We presented cotton swabs bearing chemical cues to the lizards and recorded the numbers of tongue-flicks directed to swabs in 60 sec and whether or not they bit the swab. The lizards exhibited much stronger responses to prey chemicals (cricket) than to stimuli from romaine lettuce, diluted cologne (pungency control), and deionized water (odorless control). Responses to romaine lettuce stimuli did not differ from those to the two control stimuli. In further observations, there were no significant differences in response strength between deionized water and chemical stimuli from strawberry, red grape, and dandelion flower. These findings support the hypothesis that insectivorous lizards do not exhibit strong chemosensory investigation of plants that are palatable and do induce high rates of tongue-flicking and/or biting in herbivorous lizards. Although insufficient comparative data are available to test the hypothesis that plant chemical discrimination evolves in response to dietary shifts from insectivory to omnivory or herbivory, the present data and all published data are consistent with the hypothesis. The data for M. macularia suggest that plant chemical discriminations may have been absent in basal lygosomine skinks and derived in the herbivorous lygosomine Corucia zebrata.