Strike-Induced Chemosensory Searching in the Gila Monster

Abstract

Strike-induced chemosensory searching (SICS), consisting of a poststrike elevation in tongue-flick rate (PETF) and searching movements following voluntary release or removal of prey from the predator's mouth, is experimentally verified in a helodermatid lizard, the gila monster (Heloderma suspectum). This finding agrees with previous results showing that PETF and SICS are present in all families of autarchoglossan lizards and snakes studied and in families of active foragers. Since SICS was found to last at least 10 min, longer than in any squamate reptiles except snakes and varanid lizards, the duration of SICS is greatest in the clade consisting of Varanoidea (Helodermatidae + Varanidae) and Serpentes. Long-lasting SICS in this clade is consistent with the hypothesis that morphological specialization of the tongue and vomeronasal system enhancing chemosensory detection and identification of prey may be important for the evolution of long duration. However, the short duration of SICS in teiids suggests the additional importance of phylogenetic constraints. Although the gila monster is venomous, SICS in this species has not led to evolution of a strikerelease-trail strategy as employed by highly venomous sankes, presumably because the gila monster does not eat large, dangerous prey and does not use its venom to subdue prey.