Research into Grey Squirrel Control

Grey squirrels were introduced into the British Isles from North America in the late 1800’s. Since then, they have spread throughout most of the UK except for northern Scotland and Western Ireland.
This invasive, non-native species competes with native red squirrels for food and can be carriers of the squirrel pox virus (Gurnell et al 2004; Sainsbury et al 2008). Infection with this virus is usually fatal to red squirrels, which have disappeared from most of their former range as grey squirrels spread.
However, in recent years, the advance of grey squirrels has been halted by major control efforts by conservation organisations and volunteers.
Grey squirrels cause substantial damage to trees by stripping bark. The species most vulnerable include beech, oak and sycamore and typically the fastest growing trees in a stand are the most severely affected. Damage can result in timber weakness, deformation, decay, loss of apical dominance and sometimes death of the tree (Gill 1992ab; Mayle et al 2009). The amount of damage varies from year to year, but trees are most vulnerable between 10-40 years of age, after which it is commonplace to find every tree in a stand affected. A recent analysis estimated grey squirrel damage to woodland in England and Wales to be around £37m a year, due to a combination of loss of future timber value, reduction in future carbon sequestration and the annual cost of squirrel control (Royal Forestry Society, 2021). As a consequence, grey squirrel damage has become a major disincentive for investment in broadleaved woodland.