A panel commissioned by the Tasmanian Government reported that there was overwhelming evidence that the European red fox had become established on the wilderness island which is about the size of Scotland.

Their report said that an unknown number of foxes had either been deliberately smuggled into Tasmania from the mainland or been accidentally transported there.

“Some of these, and possibly their progeny, are still living in the wild in Tasmania,” it said.

Opinion had been divided on whether there were foxes in Tasmania, which lies about 300km (186 miles) across Bass Strait, south of mainland Australia. The evidence has, in the past, been tenuous and possibly the work of hoaxers.

However within the last year a fox has been found run over on a remote road in northwest Tasmania and droppings on a farm track were positively identified as those of a fox. The most recent evidence came two weeks ago when a chicken coop was raided by a fox for the first time in Tasmania.

The discoveries have alarmed conservationists, who fear that foxes will prove impossible to eradicate on such a rugged island that has great tracts of native forest wilderness. They say that rare small mammals that have become extinct on mainland Australia will now be at risk.

Tasmania is the final refuge for a list of species that have recently succumbed on the mainland, such as the eastern quoll (a native cat), the bettong (a tiny kangaroo-like creature) and the rufous wallaby or pademelon. Other species, such as the Eastern barred bandicoot, occur in high numbers in Tasmania, but are on the verge of extinction on the mainland largely due to the fox.

The report — prepared by the Invasive Animals Co-operative Research Centre — said foxes also posed a multi-million dollar threat to Tasmania’s agricultural industry, a mainstay of the island’s economy.

Tony Peacock, the centre’s chief executive, said: “The evidence is pretty overwhelming that foxes have been in Tasmania from around about 2000. And that is using a variety of techniques, not just sightings. That is actual bodies, DNA tests from blood and from scats.”

One theory for their accidental introduction is the possibility that foxes known to roam the Melbourne waterfront may have climbed aboard freighters bound for Tasmania.

Wildlife experts believed that vicious Tasmanian devils — the world’s largest carnivorous marsupials which grow to the size of small dogs - may have been responsible for destroying foxes smuggled into Tasmania in the past. However, the devils themselves are being struck down in large numbers by a fatal cancerous disease.

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