Grey squirrel control has been carried out on Anglesey since 1998, and although this work is aimed at conserving the native red squirrel population, it also offers other considerable biodiversity benefits. Grey squirrels are a destructive pest in both wild woodlands and also commericial timber plantations. They also consume birds eggs and chicks, and there is growing evidence that this predation is exacerbating the decline of many woodland song-bird species.

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Bark stripping by grey squirrels

Grey squirrels can be very destructive in woodlands. They strip bark from the trunk and branches of trees, especially from species such as sweet chestnut, beech, sycamore and oak. However, they will also damage coniferous species such as pine, larch and Norway spruce.

Damage varies across sites and between years and levels can be difficult to predict in advance. Timber crops are often at high risk when aged between 10 and 40 years, but almost all ages of trees are potentially vulnerable. Bark stripping damage reduces timber quality in a number of ways. The wood can have heavy staining as a result of fungal infection of damaged bark, and structural defects are also frequent. These both ultimately reduce and degrade timber value. In addition, damage to the bark and the tissues within (cambium and phloem) often leads to a reduction in yield, or to put it more simply, the tree does not grow as quickly. Weakened stems may break in the wind and any trees that are ring-barked (where the bark is chewed right around the stem) will die from that point up.

The impact of bark damage reduces stand productivity and therefore the profitability of the crop. In wildwoods, bark-stripping activities may gradually change the species and structure of the tree canopy, which will result in associated changes in the biodiversity. Those tree species that are prone to grey squirrel damage will become less frequent.

The only current means of preventing unacceptable damage is for foresters to reduce the number of grey squirrels. This is done by shooting, trapping or, in counties where red squirrels do not occur, through the use of poison bait in special hoppers. Mainland sites, such as the Forest of Dean, are taking steps to maintain grey squirrels at relatively low numbers, but they can do little about the influx of grey squirrels from neighbouring woodlands.

On Anglesey, we have an opportunity to eradicate grey squirrels and therefore remove the problem once and for all. Current local government targets are to increase the woodland area on the island substantially within the next five years, and in parallel, Coed Cymru and Anglesey County Council are trying to encourage local landowners to establish more shelterbelts and woodland corridors. The removal of grey squirrels is an essential component in this, and to that end the Anglesey Red Squirrel project is seeking financial support from Forestry Commission Wales.

Useful Downloads:

The European Squirrel Initiative have produced a GREY SQUIRREL REVIEW document and the chapters relating to grey squirrel damage can be downloaded below:

Chapter 4: Environmental and economic damage [PDF File]

Chapter 5: Methods of grey squirrel control [PDF File]

Chapter 6: Financial implications of grey squirrel damage [PDF File]