Boomer, one of the devils from the Healesville Wildlife Sanctuary in Victoria, is released on Maria Island on Tasmania's east coast. Credit:Peter Mathew And then, 3000 years ago, Tasmania's devil population plummeted to just a few hundred. At the same time, the species disappeared entirely from the mainland. According to Jeremy Austin, associate professor at the Australian Centre for Ancient DNA at the University of Adelaide, three factors were most likely responsible – climate change, the arrival of dingos (which never reached Tasmania) and a human population that was growing in size, becoming more technologically advanced and shifting from a nomadic to a more settled lifestyle. Thus it was that Tasmania became the devil's last refuge. Fast forward 3000 years, and some of Australia's leading scientists are proposing that the mainland return the favour with a homecoming of sorts – by bringing Tasmanian devils back to Wilsons Prom. That is, of course, if anyone can convince the Tasmanian government to stop keeping wild devils all to itself. A decade ago, most scientific models predicted that, because of the facial cancer, the devil would be extinct by now. "The models were actually quite good," says Chris Johnson, professor of wildlife conservation at the University of Tasmania's School of Biological Sciences. "It was only out by 5 per cent."

Wilsons Promontory has been suggested as a good site to introduce the species to the mainland. But that 5 per cent – the proportion of Tasmania's pre-DFTD devil population that survives – is everything when it comes to the survival of a species. "Even in those parts of Tasmania that have had the disease there for the past 20 years, the devils are still there, albeit with low abundance," Dr Johnson said. "They are managing to persist in the face of the disease. That certainly doesn't mean there's nothing to worry about. The devil is now an endangered species, and endangered species are vulnerable in the long term for all sorts of reasons, including the potential for the emergence of another disease." A Tasmanian devil called Big John growls from the confines of his new tree house as he makes his first appearance at the Wild Life Sydney Zoo. Credit:AP And so it has come to pass. Late last year, a second transmissible cancer was discovered, one that could easily finish off devil populations just as they begin to show the early signs of developing a resistance to the facial cancer.

Which is, of course, why the clamour for reintroducing devils to the mainland is growing louder – a healthy devil population on the mainland could be one of many strategies for saving the devil, adding to the insurance policy that already exists in the form of more than 700, apparently healthy, devils held in captive breeding programs in places such as Healesville Sanctuary and Devil's Ark at Barrington Tops in northern NSW. But there is more to this whole idea than saving the devil. Reintroducing Tasmanian devils to mainland Australia, so the argument goes, would have a radical impact upon mainland Australia itself. For a start, it would, most scientists believe, help to drive down or control populations of foxes and feral cats. According to the Australian Wildlife Conservancy, feral cats alone kill an estimated 75 million native animals every night. It would also put a brake on those populations of native animals – among them swamp wallabies and common wombats – whose populations down at the Prom and elsewhere are growing unchecked and wreaking havoc on native vegetation that provides cover and habitat for a host of smaller native mammal species. "In principle, the idea has value," says Atticus Fleming, the AWC's chief executive. "But it is very important to be clear about the objectives and we think it works on two levels. First, as an insurance policy for the devil itself. Perhaps even more importantly, it would help answer the question whether a relatively large native predator, in this case the Tasmanian devil, can help to curb populations of feral cats and foxes that are killing so many native animals," Fleming said. "That said, it is premature to talk of devils becoming established right across Australia. We don't yet know whether that is viable or even a good thing, whether for the environment or for the Tasmanian devil itself."

There is little argument, however, that Wilsons Promontory is a good place to begin. "Wilsons Prom is an excellent opportunity because it was connected to Tasmania not long ago at all," says Euan Ritchie, senior lecturer at Deakin University's Centre for Integrative Ecology and a supporter of the plan to bring devils back to mainland Australia. "Environmentally speaking the Prom is very similar to areas in Tasmania that the devil currently occupies. The Prom has big problems with herbivores – too many swamp wallabies, too many wombats and introduced predators such as cats and foxes. It has threatened mammals – bandicoots, potoroos and so forth – that are eaten by cats and foxes. It's also ideal because it has an isthmus, roughly five kilometres wide, so if you really wanted to, you could just fence off the isthmus that goes to the Prom and keep devils on the inside." By restoring native predators to an ecosystem, Dr Ritchie argues, "you're letting nature take care of itself rather than having to constantly intervene". And the result may well be a more stable, more resilient ecosystem, "one where you don't have to constantly try and poison foxes or shoot rabbits or control this or control that, which is what we do so much of". And you don't have to go far to see what he's talking about: "The Mallee is a perfect example. We go to the Mallee and we shoot dingoes because they occasionally eat some sheep. Then we find that we have a fox problem, so we shoot the foxes, because they cause the same problems.

"And then we wonder why we have a kangaroo problem or a feral cat problem. You think, hang on, what actually controls a lot of that? Dingos. We're like the little boy with his finger in the dyke, rather than thinking about the whole picture." There is, of course, one problem that could derail the whole idea: Tasmania's government, whose approval would be required for any such proposal to proceed, remains resolutely opposed to the idea. According to one expert with experience of dealing with governments on the issue but who refused to be named, for any plan to proceed at Wilsons Prom "it would probably have to come from the Victorian government and the Tasmanian government would have to support it, or at least be willing to relinquish control of some of the devils in the captive breeding program to allow it to happen". When approached for comment for this article, a Parks Victoria spokesperson played a straight bat: "A decision to establish a mainland population would need to be made collectively by the federal, Tasmanian and Victorian governments." But the same unnamed expert suggested that it is the Tasmanian government that is dragging its feet: "There are quite a few people within the Victorian government who would quite like to develop this as a formal proposal, but when that's happened before the Tasmanians have just said 'no, we're not going to talk about this. Don't even bring it up'."

The terse response by a Tasmanian Department of Primary Industries, Parks, Water and Environment spokesperson to an inquiry by Fairfax Media appears to confirm this view: "The release of devils onto the mainland is not part of the Save the Tasmanian Devil Program recovery program. The focus is securing the future of the devil where it belongs in the wild in Tasmania. The Tasmanian government does not support any proposal for an introduction of devils to the mainland. Such an introduction is not required to secure the future of the Tasmanian devil." This unwillingness to even consider plans to reintroduce devils to the mainland is, of course, precisely why there are no formal proposals on the table, even as such a plan remains firmly on the agenda of everyone except the Tasmanian government. Some supporters of the reintroduction plan, like Dr Austin from the University of Adelaide, defend the position of the Tasmanian government by pointing to the plan's potential pitfalls. "One of the risks is that you put them onto the mainland and something just comes along and eats them all. We're trying to save Tasmanian devils and we've actually killed healthy animals in the process. Or they go and eat something that is itself threatened, and in the process of trying to save Tasmanian devils you've driven something else to extinction. Those of us working in universities are able to argue the theoretical case for and against reintroduction to the mainland, but ultimately it's people in government who will take the blame if things go wrong in practice."

Johnson, another advocate of reintroducing devils to the mainland, puts it another way: "The Tasmanian government is doing a good job in many respects in saving the Tasmanian devil. But surely we should be able to do two things at once?" Others are less charitable. "There's definitely some politics being played," says Ritchie. "What upsets me about that attitude is that this should be a national issue. This is not a state-based issue. We're talking about an Australian species." There is, however, a precedent that suggests the Tasmanian government's refusal to even entertain the idea may have more to do with parochialism than smart science. In 2012, the Tasmanian government oversaw the release of around 30 healthy Tasmanian devils onto Maria Island, off Tasmania's east coast. Around 100 devils now inhabit the island and the Tasmanian government frequently touts the success of the program as integral to its bid to save the Tasmanian devil from extinction. According to Chris Johnson, the lessons from Maria Island are simple: "We learned that it's reasonably straightforward to do. The mortality of devils was quite low. And they started to breed quite soon."

In any event, any reintroduction would, says Johnson, be "a controlled experiment, and not just something we do because a few people think it's a good idea". Ritchie agrees: "You do it in a controlled way, in a small area, you monitor what happens. If it goes pear-shaped, of course, you pull them out. With the devils, of course, you could easily put collars on them and track them. You're not just going to let them out and hope for the best." Ritchie goes further. "There is a general risk aversion in this country to doing these things, because something could go wrong. But one of the greatest risks facing conservation in Australia is doing nothing. It's the old saying – the definition of insanity is to do the same thing over and over again and expect a different result. That's what we still do a lot of in conservation management. Here is a different approach." And if it works, Ritchie highlights the plan's potential to inspire in Australians a whole new way of looking at their own backyard. "So much of what you read about in the news, especially when it comes to Australia's mammals is – extinct, extinct, extinct, getting worse, becoming extinct," he said.

"This is an opportunity to say we can actually do something positive. We can't go back and recreate everything. That's just not possible. But we can improve a lot of things. So maybe people can go down to Wilsons Prom and see these animals that disappeared thousands of years ago and we can bring them back. That's pretty exciting."