GROVES of hazel trees cover the Roero hills to the south of Turin. In the autumn, the nuts are gathered and mixed with chocolate to make the sticky paste Nutella which has been the breakfast treat of generations of Italian children.But now an alien invader with a voracious appetite for hazelnuts threatens to devastate the orchards.
The American grey squirrel has had a foothold in mainland Europe for almost half a century. In 1948, two pairs of squirrels were released at Stupinigi just outside Turin. But this is not prime squirrel territory, there were few trees around the release site and it took time for the animals to spread.
Now, however, they are within 15 kilometres of the Roero hills. They are also just 10 kilometres away from the lower slopes of the Alps to the north of Turin. Once grey squirrels get into these mixed woodlands there is nothing stopping them until they reach Denmark, according to Peter Garson of Newcastle University’s department of agriculture and environmental science.
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Garson is part of an irregular army of scientists, foresters and amateur squirrel enthusiasts who are fighting to push back the grey squirrel in Britain and to save the native red species. The Italians, he says, have been slow to wake up to the threat posed by grey squirrels. The Roero hazel crop alone is worth over £10 million to the local economy and the industry will be demolished if grey squirrels move in. And the damage grey squirrels do to young trees will be matched with a decimation of the red squirrel population. “The Italians have got an unexploded bomb,” says Garson.
Garson and other scientists who have been trying to stem the tide of grey squirrels in Britain for decades, may have some lessons to offer the Italians. Here, grey squirrels have already pushed the native reds close to extinction. There are just 160 000 reds left against an estimated 2.5 million greys. Now the larger greys are encroaching on the red’s last refuge, conifer plantations in the Grampian mountains of Scotland and on the border with England. Isolated populations in North Wales, Lancashire, Cannock Chase and Norfolk are shrinking and even populations on islands like the Isle of Wight are under threat.
And in Ireland, where grey squirrels were introduced around 1913 – almost a century after they came to England – the decline of reds lags behind the rest of the British Isles by just 30 years, according to Denis Tangney, a researcher at Queen’s University of Belfast.
Saving Britain’s red squirrels is likely to be expensive in time and effort – and success is far from certain. But, says Peter Kirk of the Borders Squirrel Management Group, the effort will be worthwhile. “Its simple. The red squirrel is part of our heritage. It belongs here and the grey squirrel doesn’t.” However, supporters of the red squirrel are well aware that time is running out. “It’s three minutes to midnight – we have to act now if we are going to save it,” says Keith Jones of the Forest Authority for Cumbria and Lancashire.
Conservationists have joined forces with timber growers to tackle the problem. Decades of research leave them in no doubt that alien grey squirrels are here to stay, but in October the group, working within the government’s Joint Nature Conservation Committee, agreed a strategy which might just save the native red squirrel from extinction. Money is limited but already large numbers of volunteers are helping to monitor local changes in squirrel populations, and conservationists want to persuade private landowners, who own 90 per cent of the country’s broad-leaved woodland, that it is in their interests to keep greys out.
Fussy eaters
The conservation strategy takes a three-pronged approach. First, habitats can be adjusted in areas where red squirrels already live to give them a greater chance of survival than the greys. Secondly, local conservation groups can help by putting out food hoppers that give the more fastidious red squirrel a chance to survive shortages of its normal food. More controversially, grey squirrel populations will have to be controlled, particularly those that live on the boarders of red strongholds.
According to Tom Tew of the Joint Nature Conservation Committee, the long-term goal is to change the ecology of woodlands to tip the balance in favour of red squirrels. Although the strongest red populations live mostly in conifer plantations, the animals need a mix of tree species to provide food throughout the winter. Greys are far less fussy – if necessary they can survive on acorns, which reds seem to find indigestible.
Unfortunately, over the past 50 years, the trend has been to plant large areas of conifer forest. Much of this new woodland is sitka spruce which produces small seeds and sheds them early so there is little food for red squirrels in late winter. The conservationists are trying to encourage commercial foresters and private landowners to maintain a mix of trees of different ages containing plenty of Norway spruce and Scots pine which shed their seeds late. There would then be a succession of mature trees producing plenty of seeds throughout the winter.
The Joint Nature Conservation Committee acknowledges that this type of forestry management has commercial implications. Their strategy document states that changing the mix of trees to suit red squirrels may “conflict both with economic best-practice and other nature conservation priorities. Therefore it is necessary to identify and prioritise key geographical areas for red squirrel habitat management.”
The strategy will cost foresters in time and effort because they will not be able simply to plant thousands of acres of a single species and then fell the trees a few years latter as if they were slow-growing wheat. But there is one advantage of encouraging red squirrels – they do less damage to timber plantations than greys. Reds are far less rapacious and live at lower densities. Because the grey is more efficient at exploiting food sources, population density is usually between 2 and 8 per hectare, whereas the maximum population density of reds is little more than 1 per hectare.
Red advantage
But even commercial timber growers can do something at little expense. Already, growers tend to break the monotony of endless pine forests with a scattering of deciduous trees. The grey’s catholic tastes mean that it can easily outcompete the more choosy red in mixed deciduous woodland. But foresters can give red squirrels an advantage over greys if they are careful which species they plant. For example, trees with small seeds such as birch or rowan are less likely to attract grey squirrels than species with large seeds such as oak and beech.
While woodland habitats are being altered, many red squirrels will continue to rely on food left for them in specially designed hoppers which cannot be used by greys. And in future similar hoppers could also be used to protect populations of reds from encroaching greys. Conservationists have come to realise that the two kinds of squirrel cannot live side by side. Not only is the food supply of reds threatened by greys, but veterinary scientists now believe that part of the reason for the grey’s success is that the animal carries a virus which usually only causes disease and death in red squirrels (This Week, 14 October 1995).
So how might buffer zones around red territories be maintained? Shooting and trapping are expensive and ineffective ways of controlling grey squirrels. Conservationists believe that the best solution is to use bait containing warfarin, a poison which stops the blood coagulating so its victims die of internal bleeding. If this were placed in hoppers with flaps that only an animal as large and inquisitive as a grey squirrel could open, the risk of poisoning red squirrels and other wildlife would be minimised. Although such a hopper exists, regulations controlling the use of warfarin mean that it can only be used in counties where there are no red squirrels.
Last May, the Forestry Commission, which designed the hoppers, asked for permission to test their safety. In an absurd Catch 22, the authorising agency, the Pesticides Safety Directorate, refused to grant a licence for the trials to go ahead until the relevant rules (the Grey Squirrels (Warfarin) Order 1973) were amended. Meanwhile, the Ministry of Agriculture, Fisheries and Food said that it would not change the legislation until there was scientific proof that the new hoppers worked.
The Timber Growers Association is impatient with this bureaucratic muddle because it believes that the existing law allows ministers to approve the use of warfarin in Scotland and other previously restricted areas. It is calling for this approval to be given immediately.
Meanwhile, people trying to protect red squirrels have a tough job persuading the public that poisoning grey squirrels is necessary, at least until a more humane method is found. Most people have never seen a red squirrel and have come to like its American cousin. In urban areas particularly, many people encourage squirrels to feed in their gardens. They do not like the idea of these creatures dying a slow and painful death.
Poisoning is an equally controversial issue in Italy. There, poison can be used only to control pest species such as rats and mice. Luc Wouters, an ecologist from the University of Antwerp, based in northern Italy, points out that at the moment grey squirrels do not fall into this category. Pressure from landowners for a change in the law to allow poisoning may only build up when the grey squirrel begins to cause serious damage, says Italo Currado, a professor of environmental sciences at Turin University. By that time it could be too late.
In the long term, the British Forestry Commission is banking on a more sophisticated and humane alternative to poisoning. It is sponsoring a research project at Sheffield University to find a method of making grey squirrels sterile using a vaccine in food. Immunosterilisation involves creating a vaccine from a protein on the surface membrane of a sperm cell. Inside an inoculated animal, the protein acts as an antigen generating an immune response. The vaccine could sterilise both male and female squirrels, because males would produce antibodies to their own sperm, causing the cells to clump together, and females would have an immune response to any sperm entering their body from unvaccinated males.
Harry Moore, professor of reproductive biology at Sheffield University, says that the hardest task is to identify a suitable protein – one that is found only on grey squirrel sperm cells. The antigen must generate a strong immune response in greys but not in other species eating the vaccine. And because the bait may remain for some time in a food hopper, it is essential that it does not deteriorate. Even if researchers can achieve all this, there is no guarantee that immunosterilisation will cause lifelong sterility.
At the moment, the technique is untested but Moore says that the success of the campaign on continental Europe using vaccine baits to control rabies in foxes suggests that it could work. If around 80 per cent of grey squirrels could be inoculated, the population would fall dramatically in subsequent years. Moreover, the method would be humane. It would have little effect on squirrels except to make them sterile.
Last chance
Conservationists including Wouters believe that the Italians cannot afford to wait for a vaccine if they are to stop the situation getting out of hand. Although government officials have now recognised the seriousness of the problem, they say it is a regional issue. The regional government, in turn, has passed the buck to the provincial authorities.
Wouters, however, thinks the bureaucratic log jam may soon start to shift. In September, the influential government Institute for Wildlife Management announced that it considered the eradication of grey squirrels as a major priority. Funds to support an eradication programme should now be available from the provincial authority’s budget.
The local branch of the Worldwide Fund for Nature says it would only support “bloodless control” – in other words, trapping. But experience in Britain shows this doesn’t work. Can the Italian authorities afford to be squeamish? Wouters thinks not. While the grey squirrel is confined to patches of woodland around Turin eradication using poison is still feasible. But, he says, once it starts spreading through the Alpine woodlands that chance will be lost.