Evidence of Food Chemical Discrimination in Tuatara (O. Rhynchocephalia): Comparison with a Gekkotan Lizard (O. Squamata)

In lizards, chemical senses play important roles in ecology and behavior. Previous studies have shown that food chemical discrimination, phylogeny, and foraging modes are associated in squamates. The two major clades, Iguania and Scleroglossa, display marked differences in foraging behavior. A large majority of iguanians are primarily ambush foragers and lack prey chemical discrimination, whereas scleroglossans, mainly active foragers, are capable of prey chemical discrimination. However, evidence for prey chemical discrimination in tuatara (Sphenodon), the only living representative of the order Rhynchocephalia (the sister group of Squamata) is not clear. Here, we compare responses to food chemical stimuli between Tuatara (Sphenodon punctatus) and a gekkotan lizard, the Common Gecko (Hoplodactylus maculatus). We found that tuatara showed the same responses as Common Geckos when presented simultaneously with a series of stimuli: they spent more time in the prey zone (odor of mealworms) than the pungency or control zones; they bit only the prey stimulus; and they showed similar latency to bite and give-up time as geckos. However, unlike Tuatara, geckos showed lingual sampling (tongue flicking) toward the prey stimulus. We showed that Tuatara could use chemosensory cues to detect prey in the absence of stimulus movement. Consequently, the coding of traits used to characterized tuatara as an outgroup in chemoreception studies should be revised.