Tongue-flicking and biting in response to chemical food stimuli by an iguanid lizard (Dipsosaurus dorsalis) having sealed vomeronasal ducts: Vomerolfaction may mediate these behavioral responses.

In the iguanid lizardDipsosaurus dorsalis, chemical food stimuli were discriminated from other odorants by vomerolfaction. This was demonstrated in a 2 × 3 experiment in which groups of lizards with sealed vomeronasal ducts or sham-sealed vomeronasal ducts responded to carrot chemical stimuli, cologne, and distilled water presented on cotton-tipped applicators. Abilities to detect and discriminate food chemicals were abolished in lizards having sealed vomeronasal ducts. For tongue-flick attack score and number of lizards biting, the sham-sealed group responded more strongly to carrot stimuli than to the control stimuli, but the group having sealed ducts did not. Lizards having sham-sealed ducts responded more strongly to carrot stimuli than did lizards having sealed ducts; responses by the two groups of lizards to control stimuli did not differ. Tongue-flicking occurred when the vomeronasal system detected a chemical stimulus from either carrot or cologne. Biting occurred only when the vomeronasal organ detected food stimuli (from carrot). Most duct-sealed lizards opened their mouths, some repeatedly. Mouth-opening thus occurs when the vomeronasal organ does not detect chemicals. It may be an attempt to stimulate or prime the vomeronasal organ or to dislodge the sealant.