Grey squirrels

First issue May 1997

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We have a love-hate relationship with grey squirrels. Children love to see them even if they are stealing food from the bird table. Yet they also have a bad reputation for damaging trees, raiding birds' nests or even damaging our lofts, and because they may have driven out our native red squirrels. Do they deserve their reputation? If so, what can we do about it?

How the grey squirrel arrived

The grey squirrel is a native of north-east America, its range stretching from Quebec down through New Jersey and Pennsylvania, and west to Ohio. It was first recorded in Britain in the 1820s, but systematic introduction began in 1876 when Mr T. V. Brocklehurst liberated a pair in Cheshire. More introductions followed sporadically, and the history of one of those shows how quickly the new arrivals colonised. A pair were released at Loch Long in 1892 and within 25 years grey squirrels had spread to the eastern side of Loch Lomond and into Stirlingshire - an area of 300 square miles!

There was a further wave of introductions in the first three decades of this century, and today the animal is widespread throughout southern England, apart from the Isle of Wight, and Wales, and is spreading across northern England. It is also common in parts of lowland Scotland and Ireland, and is still extending its range.

Why was the grey squirrel introduced? This is a fair question because the animal has no redeeming features compared with the resident reds, and it certainly has more vices. The most likely answer is that acclimatisation of species, as they called it, fitted in with the Victorians' view that man's task was to reshape the world in all its aspects and it became the fashionable thing to do. At that time very few people, including most of the experts, were aware of the damage that this might cause to native wildlife.

Profile of the Grey Squirrel

The grey squirrel's diet consists mainly of nuts - especially acorns, beechmast, chestnuts and hazelnuts - but they eat a variety of other foods, including fruit, cereal crops, fungi and roots. They also eat the buds and shoots of many trees, and in hard times strip the bark - this has given them a bad reputation with foresters. They attack hardwood trees from twenty to forty years old, and especially sycamore and beech. They remove bark from the main stem or from branches to get at the bast and cambium layers below, which they eat. They do this in spring and summer, probably because of temporary food shortages.

If completely encircled, the tree often dies above that point, although generally native trees survive by throwing up new shoots from below the injury. Even if it survives, though, the value of the tree as timber may be severely reduced and it is for this reason that the Forestry Commission uses poisoned bait and other methods to kill grey squirrels in its woods.*

They do not hibernate and may be seen searching for food at any time of the year. They can also often be seen burying nuts for later use, apparently at random.

The most characteristic sign of their presence is their drey, an untidy-looking nest of twigs lined with grass, leaves or moss. It is usually built in the fork of a tree between 6 and 15m from the ground. They also nest in tree holes and roofs

One-year old females have one litter per year but older females may have two. They average three young young per litter, born usually between January and April and from June to August after a gestation period of 30 to 40 days. They have no natural predators in England and usually live for 8 or 9 years.

*A report from the League Against Cruel Sports challenges the need for this on the grounds that too little damage is caused to justify the cost and cruelty involved.

Did it displace the native red squirrel?

Although the rise of the grey squirrel coincided with the decline of the red, the range of the red squirrel was already contracting before the grey squirrel was introduced, probably because of an epidemic of virus disease and loss of suitable habitat. So in most cases the greys moved in to fill existing gaps rather than driving the reds away. Whether the reds would have recovered to their former numbers without the greys we will never know for certain, but it is likely that competition from greys has prevented them from doing so.

The grey is bigger and more robust than the red, and has the advantage that it can digest acorns more efficiently. It is found in broad-leaved woodland and in mixed woodland with a good proportion of broad-leaved trees. The red squirrel belonged originally in conifer forests, but is also found in broad-leaved woodland and had adapted to living close to man in parks and gardens. Its lighter weight gives it an advantage in conifer woodlands because it is able to get out on to thinner branches to reach fir cones - seeds of spruce and pine make up most of its food. It is also found in wooded regions right across mainland Europe apart from Iberia.

Stemming the grey tide

Conservationists now believe that the advance of the grey squirrel into red squirrel territory is impossible to stop through killing programmes because they breed so vigorously and that it is better to concentrate on creating conditions that favour reds. It is too late to do anything in Essex where there are no red squirrels left, but action is being taken by Wildlife Trusts in areas where isolated populations of red squirrels are still clinging on.

A programme called Red Alert has been launched by the Wildlife Trusts in Northumberland, Durham and Cleveland, along with a number of other partners including the Forestry Commission. The programme began by carrying out research to find out exactly how greys and reds interact and how they feed. This led to practical management programmes designed to make woodlands more favourable for the red squirrel. A further Red Alert programme has been started in the North West, Breckland and Isle of Wight where populations of reds remain.

How should I control them?

In Essex there is little, if any, justification for destroying grey squirrels because their places will quickly be taken by other greys. Individual action is most unlikely to be effective because even major extermination campaigns undertaken in the past have met with little success. In the 1940s and 1950s, for example, agricultural committees handed out free cartridges to squirrel-shooting clubs and paid a bounty for every squirrel killed - all with no visible impact on the grey squirrel population. The only time grey squirrel numbers have dropped appreciably was in 1930-31 when a virulent disease killed large numbers, just as myxomatosis reduced the rabbit population in the 1950s.

The best policy, then, is to find a way of living peacably with grey squirrels, and below we suggest some things you can do to achieve that.

• Squirrels will set up their nests (known as dreys) in a roofspace if they can get in. To prevent this make sure in autumn or early winter that it is physically secure - blocking any gaps with well-secured boarding or netting. It is important to do this before they actually set up house - once they have made this commitment it is much more difficult to keep them out. Winter is also the best time to poke out their dreys if you want to keep them from nesting in your trees.
• Squirrels are no threat to young trees (which are at risk from rabbits or deer) but they may become a threat if you are planting beech or sycamore as a timber crop. Damage can be limited by planting trees close together so that they do not produce enough sap to be attractive, although this also reduces the value of the crop as timber. The Forestry Commission can advise on control measures.
• If you want to prevent squirrels from taking food put out for birds then you are in for a battle of wits because the ingenuity and persistence of grey squirrels is legendary. The Trust sells specially designed feeders, but these are not foolproof and the only safe claim is that they will deter most squirrels. One popular design consists of a mesh seed container inside a cage whose bars are narrow enough to admit birds but not squirrels. Bird tables can also be obtained fitted with special baffles and other gadgetry. Even if these do not keep all squirrels out, at least you can get some pleasure and interest from watching them work out how to get round the obstacles.