An evaluation of feral pig trapping

Abstract

The size of feral pig populations that survive conventional (food bait) trapping campaigns on two sites, and the tendency of trapping to preferentially remove sows, were examined. The use of traps containing oestrus-induced sows to enhance the trapping response obtained with conventionally baited traps was also investigated. Estimates of percentage reduction achieved by conventional trapping on the two sites were derived from two indices, proportional bait take and spotlight counts, using index-manipulationindex measures of pig abundance. Proportional bait take indicated reductions in pig abundance of 100% in 16 nights and 93% in 14 nights for the two sites from conventional trapping, while spotlight counts estimated reductions of 81% and 83%, respectively. Sex ratios of pigs on both sites were at parity prior to trapping, but strongly biased in favour of males after trapping. There was a coincident female bias in the sex ratio of trapped pigs. Subsequent to conventional trapping, no pigs were trapped using oestrous sows as bait, indicating that the use of oestrous sows does not enhance the trapping response achieved using conventional techniques. Trapping data are used to derive a compartmental model of the trapping programme. The model is used to identify potential strategies for improving the efficacy of feral pig trapping programmes.