Evaluating the risk of predation for lizards constrained in live traps

ABSTRACT Live trapping (e.g. pitfall trapping or funnel trapping) is an important sampling tool for a wide range of small terrestrial animals and is one of the predominant methods for survey and monitoring of terrestrial lizards in New Zealand. As it results in the confinement of animals, methods using live trapping must mitigate risks to animal welfare. Foraging predators can kill or injure animals confined in pitfall traps (e.g. lizards); however, visitation rates of various predatory mammals are poorly understood and reported occurrences are largely anecdotal. Following an observation of a rat depredating a skink in a pitfall trap during a lizard salvage operation, we recorded the removal of bait (pear) from traps over a 24-h period and installed motion-detecting cameras to record trap visitation. Bait loss occurred rapidly over the observed period, with 77% removed after 24 h. Three rodent species were detected visiting a trap, with one ship rat (Rattus rattus) entering it and removing the bait. We suggest that operations involving live trapping of lizards should consider predator densities and carefully monitor and report trap disturbance. Further research should examine how different trapping methods (e.g. predator-exclusive trap design, baiting, and timing of trap checks) might reduce the risk of predation to trapped animals.