Predator control benefitting endangered quoll populations in NSW

Australia’s endangered Spotted-tailed Quoll is showing resilience in landscapes where long-term wild dog baiting programs have featured in NSW.

NSW Department of Primary Industries Vertebrate Pest Research Unit Senior Research Scientist Andrew Claridge said the species had recently shown to persist in farming landscapes adjacent to large conservation reserves in southern NSW where other predators, including foxes and wild dogs, are managed as part of control programs.

In an address to the National Wild Dog Action Plan Coordination Committee in Esperance, Dr Claridge said following the arrival of Europeans in Australia, habitat loss combined with competition for shelter and food resources from introduced foxes and feral cats were the primary drivers for decline in numbers of this forest and woodland dependent species.

“Since then, it’s the introduced predators that have likely further eroded quoll populations causing the species to be even more imperilled,” Dr Claridge said.

Wherever predator management programs are instigated it is important impacts on animals, such as quolls, are minimised. 

Foundational research on the potential impacts of 1080 baiting on native marsupials by Belcher 1998, Glen and Dickman 2003, Murray and Poore 2004 and Glen et al. 2007 demonstrated quolls could detect non-toxic baits and consume them – highlighting a potential risk.

Follow-on toxic baiting trials in 2005 to 2006 in NSW, to examine the potential difference between apparent risk and actual harm, used a baiting rate of 10 to 40 wild dog baits per kilometre, with the baits impregnated with a biomarker Rhodamine B. Once ingested, the Rhodamine B is absorbed and can be detected under a fluorescent microscope.

Captured Spotted-tailed quolls were fitted with radio tracking collars and monitored for bait uptake during early autumn baiting programs. 

Of the 31 collared quolls in northern NSW in 2005, 17 per cent showed a positive result for Rhodamine and there was one death, although this animal was mauled so exact cause of death could not be determined. 

Of the 14 collared animals in the region in 2006, 65 per cent were positive for Rhodamine Band and none died. 

In southern NSW, 33 per cent of the 16 collared quolls were positive for Rhodamine B and none died. 

Cremasco and Selles undertook a similar study on the Queensland-NSW border in 2008 to investigate mortality rates of Spotted-tailed Quolls exposed to wild dog baits in the field with multiple trials at different sites, testing autumn and spring baiting.

More than 70 quolls were collared and monitored in this trial with two quoll mortalities attributed to 1080 poisoning. There was no biomarker used so the interaction rates between quolls and baits are unknown. 

Dr Claridge said the findings from this collective research helped support the reintroduction of aerial baiting into NSW national parks based on likely low impacts on quolls.

“It was certainly embraced by the wild dog committees around the Monaro and beyond,” he said.

“A decade later, the NSW Government was motivated to investigate if there were any adverse impacts from exposure to 1080 baits on quolls in spring, when adult female quolls are carrying pouch young.

“The primary question related to seeing if females exposed to 1080 baits were able to raise their young and how many of the young survived through the denning and dispersal process.

“Of the studied population in southern NSW, we could see more than half the animals had had eaten 1080 baits form the Rhodamine B in their whiskers and they continued to raise their young with no evidence to indicate there had been a catastrophic loss of pouch young despite exposure to the baits. 

“Parallel research in northern NSW also showed no evidence of adult females or other animals in that population dying from 1080 baits. Animals with young in their pouch also continued to raise their young despite having been exposed to baits.”

More broadly in 2020, Cowan et al. reported nil mortality rates of northern quolls exposed to aerially delivered toxic Eradicat baits in the field.

An even number of quolls were collared at a baited and unbaited site. No quolls from the baited site died from 1080 and neither did they return a positive for Rhodamine B. However, it was effective in reducing feral cat numbers.

Dr Claridge said the research on the impact of Eradicat baits on northern quolls had delivered the same result as work done in NSW with spotted-tailed quolls and baits prepared for wild dog control. 

“When combined, these field research endeavours give a level of reassurance to people in land management wanting to actively manage wild dogs, foxes and feral cats,” he said.

“In NSW, in relation to 1080 and quolls, we have since moved on to monitoring programs for the spotted-tailed quoll along the eastern seaboard looking at the persistence of the species over time in the face of other challenges, including feral cats, foxes and wildfire.

“I like to think the issues around 1080 and the spotted-tailed quoll have now been well and truly put to bed.”

This research backed up observations by northern NSW conservationist Steve Haslam, Quoll Headquarters, where 1080 baits had no impact on the spotted-tailed quolls inside the private sanctuary’s exclusion fence. 

National Wild Dog Action Plan Coordination Committee chair Geoff Power said NWDAP had worked hard to remove the myth around the impact of 1080 on quolls.

Centre for Invasive Species Solutions North East NSW Wild Dog Facilitator David Worsley said there had been a large increase in the quoll population in the region between Pindari Dam and Kings Plains National Park. 

“They have really become quite common placed and had never been known to exist until about five years ago.”

Access more research on the impact of wild dog baiting on quoll populations here.