Lethal control of eutherian predators via aerial baiting does not negatively affect female spotted-tailed quolls (Dasyurus maculatus maculatus) and their pouch young

Abstract

<p><b><i>Context.</i></b> Outside its breeding season, the marsupial carnivore the spotted-tailed quoll (<i>Dasyurus maculatus</i>) is apparently largely unaffected by aerial baiting for dingoes and other wild dogs (<i>Canis familiaris</i>). However, the potential impact of aerial baiting during spring on female spotted-tailed quolls carrying and weaning young remains unquantified.<br/><b><i>Aim.</i></b> The survivorship of female quolls and their pouch young was investigated after aerial baiting at two sites representing the northern and southern part of their New South Wales range. The null hypothesis was that aerial baiting would not lead to direct mortality of any adult females or higher pouch young mortality over that reported in the published literature under normal conditions.<br/><b><i>Methods.</i></b> In total, nine female quolls with pouch young and eight male quolls were trapped, fitted with GPS/VHF collars containing mortality sensors and released at their point of capture. After trapping ceased, meat baits nominally containing 6 mg of 1080 and 50 mg of the biomarker rhodamine B were deployed by helicopter at both sites at the maximal permissible rate of 40 baits km^-1. We monitored collared quolls daily for 4-5 weeks for mortality then retrapped animals and sampled whiskers for evidence of the biomarker. The fate of pouch young was also followed throughout our study by examining pouches of adult females and camera trapping at maternal den sites.<br/><b><i>Key Results.</i></b> No collared quolls died. After the daily monitoring period, 10 quolls, including all six collared female quolls, were trapped at the southern site, and whisker samples taken and assayed for Rhodamine B. Seven (4 females and 3 males) tested positive for rhodamine B, indicating consumption of baits. Separate bands of the biomarker in whisker samples indicated that most animals that tested positive had been exposed to multiple baits. At the northern site, four quolls (including two females and two males) tested positive for rhodamine B from the nine sampled. Post-baiting inspection of pouches of all trapped adult female animals, together with camera trapping at den sites, showed that the development of pouch young was unaffected by the baiting. Camera trapping arrays set across both sites continued to record the animals that were exposed to baits well beyond the baiting events, including evidence of breeding in a subsequent season.<br/><b><i>Conclusion.</i></b> Our aerial baiting programs had no observable impact on the collared female quolls, or their ability to raise and wean young. These findings are consistent with results from all previous field-based experimental studies, which show no population-level impacts of 1080 baits on spotted-tailed quolls. <br/><b><i>Implications.</i></b> Land managers should not be concerned about impacts of aerial baiting for wild dogs on spotted-tailed quolls, either in autumn or in spring during the breeding season.</p>