Controlling feral goats by shooting from a helicopter with and without theassistance of ground-based spotters

The success of aerial shooting to control feral goats in arid and semi-arid environments has lead to its widespread use in rugged and more densely veg etated terrain elsewhere in Australia. In this experiment, the method's eff ectiveness with and without the aid of ground spotters to assist in locatin g goats was evaluated in such terrain in the Chandler River Gorge near Armi dale, New South Wales. The abundance of goats was estimated by applying a c orrection factor (1.45) to indices of abundance made by ground survey. Grou nd observers monitored success during the cull. Overall, only 31% of an est imated 462 goats were culled, at an average cost of $61 per goat. In all, 5 0% of the goats were in herds never seen by the helicopter crew, while the remaining 19% were individuals that escaped (17% unseen from the air) from herds that were shot at. Inconsistent culling success, combined with marked differences in the behaviour of goats in different experimental blocks, su ggested that variable prior exposure to aerial shooting had a significant a nd confounding effect on the experimental outcome. Where goats had no prior experience of aerial shooting, culling success was 40% without spotter ass istance and 59% with spotter assistance. Where there had been a history of aerial shooting the ground observers reported a marked increase in evasive behaviour, and the cull was only 21% even with spotter assistance. These re sults show that aerial shooting is not as successful in this type of terrai n as has been assumed and suggest that its repeated or exclusive use will r esult in declining effectiveness as goats learn to evade the helicopter.