The island was overrun by 7,000 non-native grey squirrels that were introduced in the UK from North America in the 19th century.

The first pair of greys were released in Henbury Park, Cheshire, in 1876 and the current UK population is around three million.

An experiment to cull the grey invaders, which are larger and more aggressive, was a complete success and fewer than 50 remain.

Dr Craig Shuttleworth, a woodland ecologist for the Mentor Mon, Llangefni, said the project was such a success it could serve as a blueprint for red squirrel conservation across the UK.

"The project started in 1998 and we could only monitor a few sites mainly in Pentraeth Forest," said Dr Shuttleworth.

"Now there's 100 adults and 50 young in Newborough Forest and about another 150 for the rest of the island.

"The most exciting thing is they've been turning up in Beaumaris, Menai Bridge and Bryn Garth.

"There aren't huge numbers but when people see them on their bird tables they are thrilled to bits.

"The most significant thing about Newborough Forest is that we were able to remove the greys and bring in the reds when there were none there at all.

"I bumped into a couple from Wigan the other day and they had come here just to see the red squirrels," he said.

An estimated 20 litters have been born this year at Newborough which is an ideal habitat for the native squirrels.

They eat the seeds found in pine cones and other trees, acorns, beech and hazel nuts.

Anglesey is now a stronghold for the red squirrel which is almost extinct in the rest of Wales, southern England and Northern Ireland.

The greys also carry a virus which they are immune to but kills the reds. Government researches are also working on an oral contraceptive to stop the increase of the grey squirrel.

Another threat looms on the horizon in a 'testosterone-charged' black squirrel which is fitter, faster and more fiercely competitive than both reds and greys.