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A looming catastrophe for the Tasmanian Devil could be averted by releasing the species on mainland Australia to prey on feral cats and foxes, which would in turn help to rebalance the continent's struggling native wildlife.
Professor Chris Johnson said Australia's "dismal" record of 20 mammal extinctions in
the past 200 years - almost half the global total - threatened to worsen with the threat facing the devils.
He said the devil population was collapsing because of a facial tumour disease and could vanish from the wild, although the species would survive through captive animals and planned insurance colonies on small islands and in large enclosures.
But the loss of wild devils would be a serious blow for Tasmania which - except for the extinct Tasmanian Tiger - had managed to maintain its mammals.
Most mainland extinctions were caused by foxes and cats. Tasmania was until recently free of foxes, but they have now established a foothold on the island.
"Tasmanian wildlife and agricultural authorities are striving mightily to suppress this small population before it explodes and wrecks the island's biodiversity and damages farming," Johnson wrote for On Line Opinion, an internet-based social and political forum.
"We must hope that they succeed, but there is a deeper problem." Johnson, professor of ecology at James Cook University's school of marine and tropical biology, wrote the award-winning Australia's Mammal Extinctions: a 500,000 year history, which argued the case for a "rebalancing" of the nation's ecology.
He said the devil was Australia's largest surviving marsupial predator, and that predators played an important role in ecosystems by helping to keep smaller predators in check.
Where there were larger predators, animals such as foxes and cats avoided their territories and lived in small numbers in habitats that offered them protection.
Both species could breed up to large numbers very rapidly and, without larger predators, become exceptionally destructive.
Mainland Australia had suffered this effect after the extinction of the marsupial lion, the later disappearance of tigers and devils, and the more recent suppression of dingoes. "Much of southern mainland Australia was thereby left completely open to invasion by foxes and cats, which proceeded to wipe out medium-sized ground-dwelling mammals," Johnson said.
He said it was possible that in Tasmania, devils may have played the same role as dingoes on the mainland, where the remaining intact wild dog populations had helped protect other native animals - such as the bilby, which had been hunted to death outside dingo territory in central and northwest Australia.
There were already indications from Tasmanian wildlife surveys that cat populations were rising as devil numbers declined.
Johnson said devils may have also previously blocked foxes from Tasmania by harassing the invaders, competing with them for food and killing their young.
But numerical superiority was important, and an explosion of foxes now could seriously hinder the reintroduction of devils to the wild after facial tumour disease had been beaten.
"So we may be watching the destruction of a crucial ecological balance in Tasmania," Johnson said.
At particular risk were the Tasmanian bettong, eastern quoll, red-bellied pademelon and eastern barred bandicoot, once common on the mainland but now extinct outside Tasmania. Johnson suggests releasing these species back on the mainland, along with a large predator to help restore its ecological balance.
If devils were released on reserves on which fox and cat numbers had been reduced, they may beat the introduced pests. "It could also turn out to be the most effective way to protect devils from the facial tumour disease in Tasmania, by setting up a healthy population far from any source of infection."
