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.

KEYWORDS:

• Camera traps
• funnel traps
• geckos
• pitfall traps
• rodents
• skinks
• survey methods

Acknowledgements

The authors wish to thank Stephen Hartley for providing cameras and helping identify rodent species. Field work was carried out by the authors with help from Shadley van Wyk and Wellington City Council who assisted with pitfall trap installation. We also thank the Nelson lab group ‘Fixit’, Kelly Hare, and Marieke Lettink for their comments on earlier versions of this manuscript. The lizard salvage and associated work were authorised under Wildlife Act Authority 71049-FAU.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

CKW wishes to acknowledge funding from Wellington City Council, Ministry for Business, Innovation and Employment Grant UOWX1601 and a Victoria University of Wellington Doctoral Scholarship.