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UBC Theses and Dissertations

Non-target interactions and humane evaluation of a captive bolt trap on commensal rodents Ryan, Erin A'tman


The Goodnature® A24 automatic rat trap is a self-resetting captive-bolt trap powered by pressurized CO₂, designed with the objective of instantly rendering animals unconscious followed by death, but little research has examined the humaneness of the trap or its potential to harm non-target mammals and birds. This study aimed to identify potential risks to non-target animals, and to evaluate its humaneness in killing target rodents. Seventeen traps, each paired with a motion-activated video camera, were deployed at two sites where rodents were present. In a 9-week study designed to assess risks to non-target animals, traps were baited but not activated, and a blocking device (“blocker”) was used in a cross-over design to evaluate its potential at reducing non-target strikes. A total of 2,282 interactions involving 33 species were recorded, with mice and rats as the most common mammals (566 visits), followed by squirrels, raccoons, skunks, and shrews. Birds were often observed (1,312 visits), but had little interaction with the trap. Raccoons and squirrels were observed either entering the trap or inserting limbs in the trap 36 times when no blocker was in place, but these interactions did not occur for traps with a blocker. Once the researchers were confident in avoiding non-target strikes, the traps were activated and recorded for 19 weeks across two different locations to evaluate humaneness. Surprisingly, only 11 trap triggers and eight kills were observed across the two locations. Of the eight kills (3 house mice, 4 deer mice, 1 grey squirrel), observations indicated immediate or near-immediate cessation of movement and apparently instantaneous death. Post-mortem analysis by micro-CT supports observations of immediate unconsciousness. One Norway rat and one grey squirrel were non-lethally struck by the trap. One deer mouse appeared to trigger the trap without obvious injury. In conclusion, the Goodnature® A24 rat trap is a relatively humane alternative to rodenticide poisons for mice in these circumstances, but further research is needed to evaluate the humaneness and efficacy for rats.

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