Eliciting conditioned taste aversion in lizards:Live toxic prey are more effective than scent and taste cues alone

Conditioned taste aversion(CTA)is an adaptive learning mechanism whereby a consumer associates the taste of a certain food with symptoms caused by a toxic substance,and thereafter avoids eating that type of food.Recently,wildlife researchers have employed CTA to discourage native fauna from ingesting toxic cane toads(Rhinella marina),a species that is invading tropical Australia.In this paper,we compare the results of 2 sets of CTA trials on large varanid lizards(“goannas,”Varanus panoptes).One set of trials(described in this paper)exposed recently-captured lizards to sausages made from cane toad flesh,laced with a nausea-inducing chemical(lithium chloride)to reinforce the aversion response.The other trials(in a recently-published paper,reviewed herein)exposed free-ranging lizards to live juvenile cane toads.The effectiveness of the training was judged by how long a lizard survived in the wild before it was killed(fatally poisoned)by a cane toad.Both stimuli elicited rapid aversion to live toads,but the CTA response did not enhance survival rates of the sausage-trained goannas after they were released into the wild.In contrast,the goannas exposed to live juvenile toads exhibited higher long-term survival rates than did untrained conspecifics.Our results suggest that although it is relatively easy to elicit short-term aversion to toad cues in goannas,a biologically realistic stimulus(live toads,encountered by free-ranging predators)is most effective at buffering these reptiles from the impact of invasive toxic prey.

Thermophilic response to feeding in adult female velvet geckos

Fluctuations in food availability occur in many ecosystems and pose challenges to the organisms that inhabit them(Berg et al.2017).Because lizards have significantly lower field metabolic rates than endotherms,they are often considered "low energy specialists"that can cope with food shortages(Brown and Griffin 2005).However,active reptiles that maintain high body temperatures during periods of low prey availability can still incur significant energetic costs because metabolic rates scale with body temperature.To reduce these energetic costs,some reptile species select lower body temperatures and/or reduce their activity levels when food is scarce(Angilletta 2009).