The grey squirrel originally comes from North America and is not native to the UK. They were introduced to the UK between the 1870s to the 1930s as exotic species in large estates and gardens. The introduction of grey squirrels has been disastrous for our own native red squirrel ( Sciurus vulgaris ). Since their introduction grey squirrels have colonised the red squirrels native woodland by competing for food, but also the grey squirrel carries a deadly virus known as squirrelpox which they themselves are immune to.

However squirrelpox has a devastating effect on our own native reds. Since 1945 red squirrel numbers have dropped drastically and now the red squirrel is only to be found in very isolated locations throughout England and Wales. Grey squirrels can cause serious devastation in both urban and rural areas. If grey squirrels are able to get into roofs of buildings, they will gnaw through materials in the roof spaces such as ceilings, wooden infrastructures, electric wires and cables, as well as tear through fibre glass insulation. This can cause fires or flooding to properties as well as damage to the structures.

In parks and forests grey squirrels strip the bark of trees, which can cause so much damage that the stripping can affect the future growth of the woodland. Another problem is that grey squirrels prey on young fledgling birds and eggs.

Currently it is estimated that the grey squirrel population in the UK is over 2.5 million. Bark stripping damage is estimated to cost the British timber industry over £40 million per annum.