Modifying the Victor® easy Set® rat trap to improve the animal welfare of stoats and ship rats trapped in New Zealand

Stoats (Mustela erminea) and ship rats (Rattus rattus) in New Zealand are targeted by trapping to mitigate their predation on native wildlife. Internationally recognized guidelines for assessing the effectiveness and welfare performance of kill traps are supported by New Zealand legislation under the Animal Welfare Act 1999. The Victor® Easy Set® rat trap was tested and passed a similar standard for killing short-tailed weasels in Canada but failed for stoats when tested in New Zealand in 2002 (short-tailed weasels and stoats are the same species). We tested a modified version of the trap in 2011-12, modified by changing the treadle trigger to a pull trigger and adding a plastic shroud to direct and align approach by animals to the front of the trap. These traps, in vertical and horizontal sets, were tested with both stoats and ship rats. During each test the trap had to render 10 of 10 animals irreversibly unconscious within 3 minutes to meet approval requirements. The modified trap passed with both species in both trap sets. All stoats were struck across the cranium whereas rats were struck either on the cranium or neck. We recommend this trap design for use by community conservation groups for targeting stoats and ship rats in New Zealand.