Comparison of the capture efficiency of a kill-trap set for brushtail possums that excludes ground-birds, and ground set leg-hold traps

• Published in: New Zealand journal of zoology 2000-01, Vol.27 (3), p.201-206
• Main Authors: Morriss, G. A., Warburton, B., Ruscoe, W. A.
• Format: Article
• Language: English
• Subjects: BMI kill traps; leg-hold traps; New Zealand; non-target species; Trichosurus vulpecula
• ISSN: 0301-4223; 1175-8821
• DOI: 10.1080/03014223.2000.9518227

Ground-set leg-hold traps are commonly used in New Zealand to catch possums (Trichosurus vulpecula), both for control, and to monitor success of control operations. These sets have occasionally caught kiwi (Apteryx spp.) and weka (Gallirallus australis), so the Department of Conservation now requires that all traps set on conservation land be placed 70 cm above the ground in areas inhabited by these species. To set leg-hold traps at this height requires the use of platforms or boards, which reduce trapper efficiency, and longer trap chains, which increase the chance of the captured possums injuring themselves. An alternative approach, which has the potential to improve trapper efficiency and address the animal welfare concerns, is to use kill traps set at least 70 cm above the ground. Tree-trunk-set kill traps (BMI 160) were compared with ground-set Victor No 1 unpadded leg-hold traps. In the first two trials, BMI traps set with plastic cubbies (161 possums/432 trap nights) recorded capture efficiencies significantly less than those achieved using the Victor traps (215 possums/432 trap nights). In trials with more rigid wooden cubbies, the capture efficiency of BMI (218 possums/480 trap nights) and Victor traps (224 possums/480 trap nights) were not significantly different. Of the 379 possums caught in the BMI traps, 367 (97%) were struck in the head or neck (the desired target location for a humane kill), and 98% were killed. Results from these trials indicate that if BMI traps are left for three or more nights between checks, their capture efficiency will be greater than that achieved for Victor leg-hold traps that must be checked every day. We conclude that there are kill traps that can be used effectively for killing possums, which eliminate the risk of traps to ground-dwelling birds, and will thus help reduce our reliance on the use of leg-hold traps.