Roles of vomeronasal organ chemoreception in tongue flicking, exploratory and feeding behaviour of the lizard, Chalcides ocellatus

Abstract

A correlation between elevated tongue flick rate and vomeronasal organ use has frequently formed the basis for studies of lizard chemosensory behaviour, although this hypothesis has not been tested directly. The relationship between vomeronasal organ use and tongue flick rate was investigated by testing ocellated skinks, Chalcides ocellatus, with normal or sealed vomeronasal ducts (which prevents chemical access to the vomeronasal organ) in a novel environment, and in their home boxes. Lizards with normal vomeronasal organs exhibited higher tongue flick rates in novel environments than in their home boxes. Lizards with sealed vomeronasal ducts exhibited significantly lower tongue flick rates than did lizards with normal vomeronasal organs, and did not demonstrate elevated tongue flick rates relative to home box levels in response to the novel environment. Therefore, elevation of tongue flick rates in response to environmental stimuli appears to be dependent on a functional vomeronasal organ. However, sealing the vomeronasal ducts did not prevent an increase in movement in novel environments relative to home boxes indicating that detection of novel stimuli and resulting exploratory behaviour do not require a functional vomeronasal organ. Prey consumption, but not prey attack, was severely impaired in lizards with sealed vomeronasal ducts, suggesting that vomeronasal system identification of objects that are attacked is important for completion of predatory sequences.