Absence of Prey Chemical Discrimination by Tongue‐flicking in an Ambush‐foraging Lizard Having Actively Foraging Ancestors

Abstract

AbstractLingually mediated detection of prey chemicals is widespread in one major clade of lizards, Scleroglossa, but rare in the other, Iguania. It is absent in all ambush‐foraging families tested and present in all actively foraging families. In Iguania, prey chemical discrimination is known only in the herbivorous Iguanidae; in Scleroglossa, it was heretofore known to be absent only in ambush‐foraging gekkonids. Because ambush foraging precludes lingual sampling of a wide area and tongue‐flicking would disrupt the crypticity ambushers maintain by immobility, we predicted that prey chemical discrimination would be absent in scleroglossans that have secondarily adopted ambush foraging. The Cape girdled lizard, Cordylus cordylus, is member of Cordylidae, a family of ambush foragers considered derived from active foragers in the Autarchoglossa, a group of scleroglossan families having highly developed lingual chemosensory behaviours. As predicted, this species did not discriminate surface chemicals of three prey species from control substances in a series of standardized experiments in which prey chemicals were presented on cotton‐tipped applicators. Thus, even in taxa having highly developed prey chemical discrimination, adoption of ambush foraging may induce loss of prey chemical discrimination, providing further and stronger evidence that prey chemical discrimination is adaptively adjusted to foraging mode.