Is there anything more stupid than the government’s plan to kill grey squirrels?

I ask not because I believe – as Animal Aid does – that grey squirrels are harmless. Far from it: they have eliminated red squirrels from most of Britain since their introduction by Victorian landowners, and are now doing the same thing in parts of the continent. By destroying young trees, they also make the establishment of new woodland almost impossible in many places. As someone who believes there should be many more trees in this country, I see that as a problem. A big one.

No, I oppose the cull for two reasons. The first is that it’s a total waste of time and money. Here’s what scientists who have studied such programmes have to say:

“To date, there has been no successful method developed in the long-term control (nor indeed the eradication) of grey squirrel populations ... a recovery in numbers was found to take place within 10 weeks of intensive culling programs.”

You pour the money in and it pours out the other side. The government’s plan to sponsor an “eradication programme” to the tune of £100 per hectare per year is futile; though it will have the effect of transferring even more public money to rural landowners.

I doubt you’ll be surprised to hear that the idea was approved by the former environment secretary Owen Paterson, whose primary mission in office appears to have been showering his chums with gold, while ruthlessly cutting any spending that might have delivered wider benefits. This was the man, remember, who almost doubled the subsidy for grouse moors.

My second reason for opposing the cull is that there is another way of dealing with grey squirrels, which requires hardly any expense, indeed hardly any human intervention at all. Unlike trapping, shooting or poisoning, it works. It is happening with extreme prejudice in Ireland at the moment.

There is a scientific term for this method. Pine martens.

Pine martens are predators native to Britain and most of Europe. They are members of the otter, badger and weasel family (the mustelids), that are at home both on the ground and in the trees. They are, to my eye, exceptionally beautiful. They look like sinuous chestnut cats with yellow bibs. Like many predators they turn out to be essential to the survival of healthy living systems.

It now seems that many exotic species, like grey squirrels, that appear to present intractable problems do so only because they are moving into depleted ecosystems. They become invasive and destructive because there is nothing left to restrain them. American mink, for example, are a major problem in Europe where there are no otters, proliferating rapidly and wiping out water voles, birds and other species. But when otters, which are highly territorial, move in, they drive the mink out. White-tailed eagles, which have recently been reintroduced to the Hebrides, but once lived throughout Britain, prey heavily on mink and, according to a study in Finland, keep them out of areas they would otherwise occupy.

There might be no grey squirrel problem – in fact there might be no grey squirrels here at all – had pine martens not been eliminated across most of their range, primarily by gamekeepers.

Facebook Twitter Pinterest Grey Squirrel (Sciurus carolinensis) sat at edge of a mossy pond drinking with mirror reflection Photograph: Drew Buckley/Alamy

If you love grey squirrels, look away now, for Ireland has become a bloodbath. The North American rodents that once occcupied the whole island east of the River Shannon are now in full-scale rout, and the reds are pouring into the territory they have abandoned. While until recently the greycoats looked invincible everywhere, in around 20 years the frontier has shifted 100km to the east. At this rate, in another 20 years the last of them will have been driven into the Irish Sea, and Ireland will have been reclaimed by the reds. (No political metaphor is intended.)

So what’s going on? Well it now seems that the reason why grey squirrels never got past the Shannon is not that they couldn’t cross the river. They can swim, and there are plenty of places in which they could move through the trees without getting their feet wet. It’s because the far side of the Shannon was pine marten territory. And pine martens love grey squirrels – in the strictly carnal sense.

Red squirrels have a simple adaptation to pine martens: they are small and light enough to get to the ends of the branches, where the martens can’t follow. But grey squirrels, which did not co-evolve with these predators, are, by comparison, lumps: slower and heavier than the native species. They are also more terrestrial than the reds – more dependent for their survival on foraging on the woodland floor. Meals on legs, in other words.

As people in Ireland have mostly stopped killing pine martens, which are now legally protected, they have begun to recolonise their former ranges. And the grey squirrels appear to have vanished into thin air. You have to read the paper published on this phenomenon last year to believe just how rapid and comprehensive this process has been. But in case you don’t, here are some extracts.

“The grey squirrel population has crashed in approximately 9,000 km2 of its former range and the red squirrel is common after an absence of up to 30 years.”

“Grey squirrel sightings accounted for less than 8% of animal sightings in [the Irish Midlands], which is remarkably low considering that they are a much less elusive species than either the red squirrel or the pine marten, and are also more commonly associated with human settlements.”

The health and weight of grey squirrels in the pine marten zone is “extremely poor,” while squirrels in an area without martens “are thriving”.

“This is the first documented evidence of a grey squirrel population retracting, without any human intervention, subsequent to having established itself as an invasive species.”

Two aspects of this story jump out at me. The first is the greys’ astonishing speed of retreat. The numbers just don’t add up: the martens simply couldn’t eat that many squirrels. As the paper points out, “it would be unlikely that a low-density pine marten population could impact a high-density grey squirrel population by direct predation alone.”

The second is that grey squirrels in the region haunted by pine martens are much thinner than those elsewhere. At first sight this makes no sense: with fewer competitors, you would expect the survivors to be fatter and healthier.

So what’s going on? Though the paper doesn’t speculate, there seems to be a likely explanation. The pine martens are creating a “landscape of fear”, rather like the one that some ecologists (though others have now challenged the claim) believe wolves have generated among deer in Yellowstone National Park in the US state of Wyoming. It’s not just that pine martens are eating the squirrels: they are terrifying the living daylights out of them.

If grey squirrels have no defences against martens, they must spend much of the time they would otherwise have spent feeding trying to avoid them. They are likely, metaphorically or perhaps literally, to spend so much time looking over their shoulders while they should be foraging during the summer that they don’t accumulate sufficient fat to get through the winter. The pine martens are starving them out.

The lesson is obvious – to everyone except the dunderheads administering public policy in Britain. If, as they claim, their aim is to eliminate grey squirrels, rather than to pour money into the laps of the landed gentry, they should abandon the useless programme of trapping, shooting and poisoning, and instead bring back a native predator.

While pine martens are once again thriving in parts of Scotland (and, surprise, surprise, these are the places in which red squirrels also survive and grey squirrels are absent), across England and Wales they are functionally extinct. This means that while there are some tiny remnant populations in a few areas (Cumbria, Snowdonia and the North York Moors for example), due to intense persecution by gamekeepers, and others in the past, their genetic base is too narrow to allow them to expand.

Re-establishing pine martens means reintroducing them: bringing new genetic stock both to the pockets in which they survive and to places from which they have been eradicated. That is what the Vincent Wildlife Trust, among others, hopes to do.

Facebook Twitter Pinterest A red squirrel in one of its last strongholds in England in Hexham, Northumberland. Photograph: Will Nicholls /Rex Features

Meanwhile, the Game and Wildlife Conservation Trust, which I see as a greenwashing agency for the shooting industry (how many conservation groups do you know that teach children to use shot guns and run courses on snaring, lamping and trapping?), is campaigning to reduce pine marten populations in Scotland. Yes, reduce.

It claims that it wants to do so to protect capercaillies: the giant grouse that also once lived across much of Britain but are now confined to a few glens in Scotland. But there is no evidence that pine martens are implicated in the capercaillie’s decline: in fact the capercaillie is doing best where pine martens are also thriving, and doing worst where the predator continues, illegally, to be persecuted.

(I wonder whether there might be a connection? Might pine martens suppress other predators that affect capercaillies? Or are both species victims of the appalling land management practised by “sporting” estates in areas like Deeside?)

The Game and Wildlife Conservation Trust’s attitude is typical of the views that have long prevailed amongst shooting interests: all too often estate owners would rather cut their own throats than tolerate the presence of predators, even when those predators are protecting them from massive problems, like grey squirrels or (due to the absence of lynx) exploding roe and sika deer populations.

Unfortunately, it is these entrenched interests and attitudes that still dominate government policy. The futile plan to cull grey squirrels was hatched at a symposium of chinless wonders convened by the Prince of Wales and Owen Paterson in one of Charles’s many properties, Dumfries House in Scotland.

This meeting took place several months after the Irish study was published. But the British establishment is almost impervious to new thinking and new information, so perhaps it’s unsurprising that this confederacy of dunces decided to pour millions into a futile gesture, rather than to do something useful. I dare say that most of them still regard pine martens as vermin anyway.

Like the army and navy in the 18th century, the governance of the countryside is still dominated by titled amateurs, while those with professional knowledge and expertise are frozen out.

So perhaps there is a political metaphor here after all. Isn’t it time that these grey and ponderous relics of the Victorian era were pushed out of policy-making, and replaced by bright-eyed and bushy-tailed people who are agile enough to respond to new situations?

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