The red squirrel is a native species, it has been present in the British Isles since the retreat of the glaciers of the last ice age -so around for some 10,000 years.  The grey squirrel on the other hand has only been here since the mid nineteenth century, when it was introduced from America.  Though relatively small numbers were introduced at stately homes, it did incredibly well and they spread out from their original sites, colonising woodlands and spreading across the country.  As the grey squirrel spread so the red squirrel retreated and its numbers declined.

Recent population estimates suggest that the grey squirrel population may now be as high as three million, whereas the red squirrel numbers are probably less than 300,000.

The grey squirrel is to be regarded as a pest.  Why ?

(a).   They strip bark from trees.   This is the main type of damage type of damage. The squirrels remove  bark to access the sap tissues underneath.

Squirrel damage

(b).   They cause the death of trees.  The damage to the bark and the underlying tissue can affect the flow of water and nutrients from soil to leaves.  It can also allow for the entry of pathogens (parasitic bacteria and fungi).

(c).   Their activities have an impact on the quality of timber that can be harvested.

(d).   They are associated with biodiversity loss, not only do they complete with and displace the native red squirrel, their presence can affect other woodland species such as songbirds (eat their eggs) and dormice.

(e).   Grey squirrels pass on the squirrel pox virus to red squirrels.  Once infected the red squirrels tend to die of dehydration and starvation.

[(f).   The grey squirrels that visit my garden dig up bulbs, like crocus, tulips and hyacinths.  They also make raids on soft fruits.]

Older damage by squirrels

There are measures to stop or limit grey squirrels from breeding.   One ‘extreme’ measure is shooting or trapping followed by euthanasia.  Another measure is the introduction of Pine Martens, they seem to control the numbers of grey squirrels whereas red squirrels have co-existed with Pine Martens in areas like north Scotland for many years.  

However, the Governments Animal and Plant agency is developing a contraceptive.  This is a vaccine based product which causes the squirrel’s immune system to render both males and females infertile.   The vaccine induces the formation of antibodies against the animals own reproductive hormones. The idea is to fed it to the grey squirrels through feeding hoppers that grey squirrels can access but not red squirrels or other animals. The bait will need to be palatable and attractive to the squirrels. Should this prove successful, it will be a non-lethal way of reducing the numbers of the grey squirrel without shooting or trapping.

For detailed information on the squirrel contraceptive project, visit https://aphascience.blog.gov.uk/2024/09/30/reducing-grey-squirrel-overpopulation/

Similarly, lots of information on squirrel damage here : https://www.observatree.org.uk/media/1425/identifying-squirrel-damage.pdf