Capture predicates corticosterone responses and a low recapture likelihood in a varanid lizard

Abstract

Context Understanding both the short- and long-term consequences of live animal capture is desirable to limit potential data biases or compromise animal welfare. The short-term elevation of glucocorticoid hormones in animals is an expected short-term stress consequence of trapping and restraint experiences. However, because these hormones also influence behaviour and memory, they may provide a physiological basis through which individuals vary in their recapture responses to subsequent trapping episodes. Aims This objective of this study was to evaluate the interplay among trapping method, corticosterone responsiveness and recapture likelihood in a lizard, the lace monitor (Varanus varius). The first aim compared how different capture methods and associated restraint durations influenced plasma corticosterone of lace monitors. The second aim evaluated the relationship between capture methodology, corticosterone response and annual recapture frequency. The third aim measured yearly estimates for the probability of lace monitor recapture. Methods Lace monitors were cage-trapped or noose-captured at 76 sampling sites across three annual sampling periods to measure capture experience, obtain blood samples and estimate recapture probabilities. Results As expected, an increased restraint time and exposure to different capture methods significantly influenced corticosterone concentrations in lace monitors. Lace monitor recapture rates were meagre, suggesting that irrespective of the capture method, restraint duration and corticosterone levels, any form of initial capture experience typically leads to long-lasting aversive behaviour. Conclusions Although plasma corticosterone concentrations may be tell-tale of a lace monitor’s duration to short-term capture and restraint, they were not associated with the recapture likelihood in subsequent trapping events. Implications Rapid and seemingly long-lasting trap aversion has apparent implications for the design of population monitoring programs used to study lace monitor population ecology.