In Australia, baiting with 1080 (sodium fluoroacetate) is widely used to reduce predation of native wildlife by the red fox. However, such control programs may place some native carnivores at risk, particularly the spotted-tailed quoll in eastern Australia. We measured the mortality in a total of 57 quolls fitted with mortality radio-transmitters during four experimental fox baitings with Foxoff® 1080 baits containing Rhodamine B in north-east New South Wales. In all experiments quolls visited bait stations regularly and removed a total of 20 baits. All but one of these baits was found in the vicinity of the bait station, indicating that quolls did not ingest baits. This was confirmed by the absence of Rhodamine B in the vibrissae of all quolls retrapped after baiting. The only quoll that may have died from a bait had eaten a cached bait some six weeks after baiting concluded. Thus, baiting did not threaten any of the quoll populations sampled. Therefore it appears that most restrictions imposed to protect spotted-tailed quolls during fox baiting are unnecessary as long as this bait type is used.
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 vegetated terrain elsewhere in Australia. In this experiment, the method’s effectiveness with and without the aid of ground spotters to assist in locating goats was evaluated in such terrain in the Chandler River Gorge near Armidale, New South Wales. The abundance of goats was estimated by applying a correction factor (1.45) to indices of abundance made by ground survey. Ground observers monitored success during the cull. Overall, only 31% of an estimated 462 goats were culled, at an average cost of $61 per goat. In all, 50% 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, suggested that variable prior exposure to aerial shooting had a significant and confounding effect on the experimental outcome. Where goats had no prior experience of aerial shooting, culling success was 40% without spotter assistance 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 results show that aerial shooting is not as successful in this type of terrain as has been assumed and suggest that its repeated or exclusive use will result in declining effectiveness as goats learn to evade the helicopter.
Warfarin bait has been used since 1986 to control introduced black rats (Rattus rattus) in palm-seeding areas on Lord Howe Island, New South Wales. We examined the relationship between bait use and mouse numbers in these areas. In the first experiment, one mouse population was manipulated by removal trapping while baiting for rats was being undertaken. When mouse density was reduced by approximately 193 ha–1, bait consumption fell by 80.0%, suggesting that the mice were not susceptible to warfarin and that the rat bait may have been an important food resource for these mice. During the second experiment, the existing rat-baiting regime was maintained in one area but manipulated in another – bait was removed for one year then returned during the second year. Under the existing baiting regime, mouse numbers increased during the two-year period. The mouse population that was denied rat bait declined to near zero after one year, then increased when bait was reintroduced to the area, reaching densities after one year similar to those in the area where bait had been maintained. We conclude that the mice were resistant to warfarin, consumed most of the bait distributed to control rats, were largely dependant on the bait as a food source, and reached high densities in rat-control areas as a direct result of rat-baiting strategies.
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