Suchergebnisse

In eastern Australia, the spotted-tailed quoll (Dasyurus maculatus) is the species thought to be most likely at risk from aerial baiting with compound 1080 to control wild dogs (Canis lupus familiaris and C. l. dingo). Although it is known that quolls occasionally die of 1080 poisoning, the broader impact on populations remains unresolved. We therefore assessed the impact of a regular aerial baiting campaign on a population of spotted-tailed quolls. Baiting with 1080 meat baits was conducted by the local Wild Dog Control Association and followed the same procedure as in previous years with the exception that the biomarker, rhodamine B, was added to the baits. Prior to the baiting, 36 quolls were trapped and fitted with mortality radio-collars; 31 of these collars were still functional at the time of baiting. Quolls were monitored from a helicopter and on the ground until retrapped 5–9 weeks after baiting. Transmitters were then removed and a sample of vibrissae was taken for rhodamine B analysis. Carcasses found were analysed for 1080. Predator numbers were assessed before and after baiting using track pads across trails. Among the initial 36 radio-collared quolls, nine mortalities were recorded during the course of the study (seven after baiting). Only one of the nine deaths could be directly attributed to 1080 poisoning. In addition, vibrissae from five of the 35 individuals sampled after baiting were marked with rhodamine B, indicating that these individuals had consumed bait, and survived. Consequently, mortality attributable to this particular aerial baiting campaign was low, apparently because few quolls ate bait and most of those that did survived. Track counts for predators indicated a significant decrease in dog and fox numbers after baiting. Cat activity remained unchanged and the number of quoll tracks increased.

More than most other animal control techniques, toxic baiting is fraught with the potential impact on non-target species. In the present study, we investigated the effect of aerial baiting with 1080 to control wild dogs in north-eastern New South Wales (NSW), Australia, on populations of southern bush rats (Rattus fuscipes assimilis) and brown antechinus (Antechinus stuartii), using a controlled experiment. Six populations, three each within widely spaced baited and unbaited trapping grids, were monitored before and after bait laying. To develop capture–mark–recapture indices, separate 4-day trapping surveys were undertaken twice before and twice after meat baits (250 g containing 6 mg sodium fluoroacetate, 1080) were delivered from a helicopter at 40 baits per kilometre. To assess non-fatal bait consumption, all baits contained rhodamine B (RhB), which gets incorporated into the vibrissae of animals that have ingested this marker. Neither mammal population decreased in size after baiting, nor was there any increase in population turnover rates or changes in the movement patterns of either species. Furthermore, no trapped animal tested positive for RhB, suggesting that these small mammals rarely consume meat baits, and that, at the population level, the impact of baiting on them was likely negligible. It is therefore unlikely that the current practise of aerial baiting in NSW, although effective in reducing dog activity, threatens populations of these two common species and perhaps small mammals in general.

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.

Between 2000 and 2002 two populations of the spotted-tailed quoll (Dasyurus maculatus) were studied on the New England Tablelands using trapping surveys and radio-tracking. Overall, 85 individuals were trapped, but only two individuals were trapped throughout the 26 months of the study. Trapping was male-biased (74%). Adult males (>1 year) were substantially larger than females. On average, males travelled longer distances than females, and the maximum distances recorded were 8.1 and 3.9 km for a male and female respectively. Home ranges of males overlapped substantially, whereas those of females appeared to be exclusive. Mortality rates and the turnover in the quoll populations appeared to be substantial and at the beginning of autumn the populations comprised ~50% juveniles.