Rate of tongue flicking by garter snakes (Thamnophis radix haydeni) and rattlesnakes (Crotalus v. viridis, Sistrurus catenatus tergeminus, and Sistrurus catenatus edwardsi) during prolonged exposure to food odors.

Garter snakes ( Thamnophis radix haydeni ) emitted more tongue flicks in environments containing fish or salamander odors than in a control environment. This indicates that appetitive searching (guided by the vomero-nasal system) can be activated by olfactory cues. Specimens of three taxa of rattlesnakes ( Crotalus viridis viridis, Sistrurus catenatus tergeminus , and Sistrurus catenatus edwardsi ) did not emit more tongue flicks in an environment containing mouse odors than in a control environment. Hence, the vomeronasal systems of these rattlesnakes were not activated by olfactory cues. A hypothesis is offered about the conditions required to stimulate tongue flicking in rattlesnakes.