EVIDENCE that foxes now inhabit Tasmania is "overwhelming", according to the island state's peak farm body.

The Tasmanian Farmers and Graziers Association is urging farmers to report any fox sightings after a University of Western Australia analysis of faecal matter detected the presence of at least three males and one female fox last year.

Invasive Animals Co-operative Research Centre chief executive Tony Peacock said more than 2000 faecal samples had been analysed and 30 were found to be from foxes.

He said the fact both sexes were detected indicated there was potential for breeding.

Dr Peacock said the foxes appeared to be concentrated near Burnie and near Spreyton, south of Devonport and it appeared one male fox was living at Burnie.

TFGA chief executive officer Chris Oldfield said there was now beyond doubt that foxes had been introduced into Tasmania.

"By implication that threatens our native wildlife, domestic animals and agriculture in general," Mr Oldfield said.

"It also threatens one of our advantages in the marketplace."

He said Tasmanians had been reluctant to accept the fact foxes inhabited the state despite evidence building since 2000.

He said the density of the Tasmanian population might be as low as one fox per 500 sq km.

"Research overseas indicates that with a density of any less than one fox per 25 square kilometres, foxes are almost impossible to find," Mr Oldfield said.

"Therefore, like the Tasmanian tiger, it is difficult to detect. But unlike the tiger, there is clear evidence that it exists."

Mr Oldfield urged farmers to report any sighting by calling the fox hotline on 1300 369 688.

"The potential damage to agriculture and to the environment generally is huge," he said. "Let's stop the problem now."