However, this may not be so in terms of the conservationists’ criterion for a native species, which is that they are presumed to be those that are present in Great Britain by natural means. In general, they migrated (or were transported by other species) into Great Britain after the last ice age, without the assistance of humans.
For some time I have been looking into the use of squirrel fur during the early medieval period and can find no record of indigenous squirrel fur being used in Great Britain.
In the later Middle Ages the central distribution point for squirrel skins from the Baltics, Scandinavia and Russia was Bruges, from where skins were imported to Great Britain via London and the eastern ports including York, which was at that time navigable from the North Sea.
Therefore, it is no surprise that the first mention of “squirrels” in England was by Hugh, the Bishop of Lincoln (later St Hugh) towards the end of the 12th century.
So a far more likely explanation for the arrival of the red squirrel in the British Isles – rather than being regarded as “native” on the strength of bone finds that appear not to have belonged to the same sub- species – is that they were imported as live animals from mainland Europe because of the well-known and recorded price fluctuations of European skins that threatened the livelihoods of skinners and tanners throughout Great Britain.
This would explain the thousands of years of no squirrel records in England and red squirrels establishing themselves in the later Middle Ages, probably in circumstances similar to that of the American mink nowadays. It is also understood that red squirrels were kept in captivity in Ireland for their fur, which was exported to mainland Britain.
Rather than the red squirrel being a “native species”, there is a much better case for regarding it as being introduced on a commercial basis by fur industry entrepreneurs as a “grow-our-own-fur” enterprise that failed because the thicker fur from colder parts of Europe and Russia was more desirable.