Dr Thomas Newsome, ecologist at Deakin University and the University of Sydney, with a dingo. Credit:University of Sydney A Department of Agriculture spokesman said the total annual cost of foxes to Australia's environment and economy is estimated to be $227.5 million. Dingoes don't pose the same risk to threatened species, as the smaller mammals have developed anti-predator strategies to co-exist with dingoes," he said. Even so, Dr Newsome said reintroducing dingoes near small populations of threatened mammals would need to be carefully controlled. The study, published on Tuesday in Nature Communications, looked at the role apex predators play in controlling the population of "mesopredators", upon which they prey.

Native animals such as the bilby have co-existed with dingoes for 4500 years, yet are threatened by introduced species such as foxes and cats. Credit:Bobby Tamayo As well as studying the impact of dingoes on red foxes in Queensland, the study examined the relationship between the grey wolf and coyote in Saskatchewan, Canada, and the grey wolf and jackal in Bulgaria and Serbia. The findings of the study suggest optimum suppression of the smaller predators occurs when the apex predator is able to exist at high densities over large areas. A feral fox in a NSW national park. Credit:NSW Department of Environment "This research shows that apex predators like dingoes and wolves need large, continuous territories in order to effectively control the balance of their ecosystems," Dr Newsome said.

He said dingoes ideally need a contiguous territory of hundreds of thousands of square kilometres for their positive impact to be maximised. Dr Mike Letnic, UNSW conservation biologist. Credit:Peter Rae "While a range of 200 to 300 kilometres across is ideal, at smaller scales there is still an impact on feral species, such as foxes and cats," he said. A co-author of the study, Mike Letnic from the University of NSW, said: "These results demonstrate that patterns we have seen in Australia across very large scales also apply in Europe and Canada." A grey wolf in Yellowstone National Park, in the US.

The data used in the study is from bounty counts from when the Queensland government paid for the culling of dingoes and red foxes. Dr Newsome said that while the data was from the 1950s, the scale provided the best basis to develop their findings. "More recent studies of dingoes at a local scale support these results," he said. He also said that given their correlation with findings in Canada and Europe they have confidence in the outcome of the study. Of course, reintroducing dingoes to parts of Queensland and NSW from where they have been removed would bring them into contact with grazing lands. Dr Newsome said if policymakers were to consider reintroducing dingoes, as has been trialled in parts of Victoria, it would have to be at large enough scales for it to have a strong impact.

"We would have to accept occasional stock losses," Dr Newsome said. "Humans need a greater tolerance of apex predators if we want to enjoy the environmental benefits they can provide." He told Fairfax Media that some modelling showed dingoes would have a net economic benefit in cattle grazing areas by suppressing kangaroo numbers, improving grass feed. Dr Newsome suggested alternative strategies could be used in sheep country, including the use of companion and guardian animals such as maremma sheepdogs, alpacas and donkeys. A spokeswoman for the NSW Office of Environment and Heritage said consideration of any proposal to reintroduce dingoes would require extensive consultation with landholders and other stakeholders concerning impacts and benefits. A federal Department of Environment spokesmansaid: "A number of research projects are considering the interactions between dingoes and foxes and feral cats. These projects will help inform where and when it may be appropriate to consider reintroductions of dingoes."

The National Farmers Federation did not wish to comment on the study. A recent video that has been widely shared on social media showed how the reintroduction of wolves in a US national park had a widespread positive effect on its ecosystem. Dr Newsome said that video, How Wolves Change Rivers, was a good layperson's overview of the impact apex predators can have when reintroduced to an ecosystem. "When wolves were reintroduced to Yellowstone National Park it helped shift the area back into relative balance," he said.

For the study Dr Newsome worked with ecologists at Oregon State University, the University of Washington, the University of Belgrade, the University of Tasmania, the University of Ljubljana, UNSW, and the University of Forestry, Sofia.