Squirrels

Disappearing native red squirrel
© Forestry Commission

The red squirrel is native to the British Isles. It was once present in all wooded areas but its numbers seem to have fluctuated widely from year to year. Since the 1920s or 30s, its range has shrunk on mainland Britain, and it has almost gone from lowland England and Wales.

The grey - or gray - squirrel from N.E. North America is slightly larger and stockier than the red squirrel. Liberated in up to 35 sites in the British Isles from around 1876 to 1920, it expanded rapidly across England and Wales from about 1930 to 1950. It is still advancing slowly northwards.

Often regarded as an attractive, mischievous animal with bright eyes and a bushy tail, the grey squirrel is a nuisance or pest in many situations.

Market gardens, orchards and farms can suffer serious economic losses when this addition to the UK fauna raids crops. It is a major pest in woodlands and forests.

Especially in early summer, grey squirrels can strip the bark from the base, stem or crowns of trees. If they remove the bark right round - called ring-barking or girdling - the upper part of the tree or branch will die.

Where smaller patches of bark are chewed off, callus tissue may eventually heal the wound but often infection has set in and the timber value of the wood plummets.

Grey squirrels seldom debark trees in their native woodland habitat in N.E. North America. In the UK, this practice is accredited to either feeding on the sugary phloem under the bark or agonistic, territorial type behaviour - but is often a bit of both.

Trees with smooth barks like beech and sycamore are particularly susceptible to attack - but most tree species suffer and the habitat is spreading.

Bark-stripping occurs mainly from May to August. Broadleaf trees are more vulnerable than conifers and trees aged 10-40 years are particularly susceptible. Sycamore, beech and oak are the most vulnerable common species but grey squirrels can potentially breed nearly all year - and climate warming will facilitate the reproductive potential of this alien species.

Grey squirrels strip the bark from an increasing number and variety of both native and introduced trees. From a forestry viewpoint, that slows growth, degrades the timber value and reduces productivity and profitability.

But the impacts do not stop there - their bark-stripping activities can start to change the species and structure of the tree canopy, particularly in beech woods in the Chilterns and Cotswolds - and with that comes associated changes in the biodiversity. The squirrels do also eat birds' eggs and nestlings, have been implicated in the decline of the native red squirrel and reportedly attack hibernating dormice.

The only means of preventing unacceptable damage at present is by reducing the number of grey squirrels by shooting, trapping or using toxic bait in special hoppers.

Grey squirrel stocks reach a far higher density than reds. A run of mild winters and good seed on most crops of oak and beech nuts means grey squirrels can breed here for most of the year, boosting their populations still further. Climate or global warming may be an added bonus for them.

The rise of the greys and fall in distribution of the native red squirrels appear linked. Disease and competition for food and space may be implicated but the picture is complex and confused.

Grey squirrel damage to beech
© Forestry Commission

Measures tried to give red squirrels a helping hand include giving them top-up food in special hoppers and tightropes strung between trees to encourage them to cross busy roads safely. Projects like "Red Alert" in the Lake District are taking action to save the native red squirrels.

Extensive blocks of coniferous forests such as Thetford are important as red strongholds. Reds will strip bark from conifers too to feed on the sap.

More:

  • FC Practice Note 4. Controlling Grey Squirrel Damage to Woodlands. B.A. Mayle (2004).
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  • FC Practice Note 5. Red Squirrel Conservation. H. Pepper and G Patterson. (1998).
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  • FC Practice Note 11. Practical Techniques for Surveying and Monitoring Squirrels.
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  • J. Gurnell, P.+ Lurz & H. Pepper. (2001).
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  • FC Info Note 76. Habitat Use by Red and Grey Squirrels (2005).

Visit the European Squirrel Initiative at

www.europeansquirrelinitiative.org