
TY  - JOUR
A1  - Choquenot, David 
A1  - Hone, Jim 
A1  - Saunders, Glen 
T1  - Using aspects of predator-prey theory to evaluate helicopter shooting for feral pig control
JF  - Wildlife Research
JO  - Wildl. Res.
Y1  - 1999
VL  - 26
IS  - 3
SP  - 251
EP  - 261
KW  - 
UR  - https://doi.org/10.1071/WR98006 
N2  - Because it achieves rapid reductions in pig density, helicopter shooting is perceived to be a cost-effective option for feral pig control. In order to evaluate the cost effectiveness of the technique and develop predictive models of variation in costs, functional response models derived from predator&#8211;prey theory were fitted to 3 data-sets describing variation in kill rates with feral pig density. The data-sets were collected during shooting programs conducted on the Mary River floodplain in northern Australia, and on the Macquarie Marshes and Paroo River floodplain in western New South Wales. Fitted models indicated that variation in kill rates with pig density took the form of a Type 3 functional response for all 3 data sets, kill rates approaching a constant maximum at high pig densities and declining toward 0 at pig densities greater than 0. While maximum kill rates were similar for the 3 shooting programs (average 60.49 kill h&#8211;1, range 49.64&#8211;76.28), densities below which no pigs would theoretically be killed varied significantly (average 2.79 pigs km&#8211;2, range 1.34&#8211;5.02). Similar maximum kill rates for the 3 shooting programs indicates that, once located, the time taken by shooting teams to dispatch pigs was relatively constant (0.023 h). Variation in threshold densities below which no more pigs would theoretically be shot, indicates that as the density of pigs was reduced, their vulnerability to shooting teams differed between the 3 shooting programs. This may have reflected differences between sites in either the capacity of resident pigs to learn to evade shooting teams or, more likely, the availability of refuge habitat. For 2 of the shooting programs, too few data were available to estimate the effect of declining pig density on kill rate, precluding detailed examination of differences in the efficiency with which pigs were found (search efficiency). Using estimates of pig density below which no pigs would theoretically be shot to set a limit to the effectiveness of shooting programs, models predicting variation in hours per kill with pig density were derived from each data set. These models demonstrated that hours per kill increased exponentially as shooting reduced pig populations below threshold densities of approximately 2&#8211;6 pigs km&#8211;2. Generalised models relating variation in cost per kill to pig density for the 3 shooting programs are described. 
ER  -

