Genetic testing has revealed that most of Britain's supposedly indigenous red squirrels are probably recent European interlopers that have left their native cousins clinging on in isolated strongholds, writes Steve Farrar.
Research has shown that the plight of the indigenous British red squirrel, immortalised in the shape of Beatrix Potter's character Squirrel Nutkin, may be far worse than previously suspected.
The native red squirrel has already been pushed from much of its former range in England and Scotland by the grey squirrel, which was introduced to the British Isles from North America.
Now it seems that since the 1980s it has also been usurped by a European variety.
Marie Hale, Peter Lurz and Kirsten Wolff, postdoctoral research associates at Newcastle University's School of Biology, compared mitochondrial DNA samples collected from 180 animals.
The red squirrel samples came from Northumberland, Cumbria, County Durham and the Scottish borders, as well as from continental Europe. A number of the samples were retrieved from animal remains dating back over the past century.
The scientists found that the majority of the population of red squirrels had a recent European origin, many coming from Scandinavia over the past 40 years.
They believe that a distinct genetic variety that dominated up until the 1980s was likely to be the native British subspecies, which had lighter coloured ears and tail than its continental cousin.
The British subspecies has now been displaced in Northumberland and is competing with the Europeans in Cumbria, where it may have been protected by the fragmentation of its habitat.
Dr Hale said the findings, which are published in the latest issue of the journal Conservation Genetics , had been a surprise.
"We suspected there would be some indication of the introduced subspecies but we didn't expect it to be as high as it is," she said.
The European red squirrel, which is largely unaffected by the grey squirrel on the Continent, has been brought to the British Isles a number of times over the past 150 years. But it was thought to have only reached the north of England in 1966.
Nevertheless, it appears to have rapidly usurped its native rival.
Dr Hale said it was possible that the European subspecies was doing well because it was better adapted to the European conifers grown in Forestry Commission plantations, like the 50,000 hectare Kielder Forest in Northumbria although further research was needed to confirm this.