North American gray squirrels may drive Britain's native red squirrels into extinction. Conservationists are now trapping and killing the gray rodents in order to preserve biodiversity.
Laura MacPherson has never seen a red squirrel in real-life, she says, "Maybe in the Isle of Skye when I was a child, but I can't remember."
MacPherson runs a bed and breakfast in Stirling, southeast Scotland. Instead of the native red squirrels, non-native gray ones roam her garden. "They can be a bit of a nuisance," she says. "They bite their teeth right through the very hardest of plastic containers, they get into your garbage, they ruin things."
Even worse, gray squirrels have pushed red squirrels to the brink of extinction. The gray ones have more babies, are bigger, eat more - and even steal food red squirrels have stored away for the wintertime.
Only an estimated 160,000 red squirrels remain in the United Kingdom, compared to about three million gray squirrels, according to the organization "Red Squirrels in South Scotland".
Red squirrels have a tough time getting through cold winters because gray squirrels steal their food
Death the only option
A banker named Thomas Brocklehurst is believed to have been the first person to bring gray squirrels from the United States to England in the 19th century. As rumor has it, the silver-colored rodents were to embellish his country house garden.
"I wish we had a time machine," Ken Neil, a conservationist, says. "Then I could go back and say: Mr. Brocklehurst, that is not a good idea!"
Neil works for the project Saving Scotland's Red Squirrels funded by the Scottish government. Three quarters of the remaining red squirrels in the UK live in Scotland.
Conservationists like Neil have set out to rid Scotland of gray squirrels - so that the red ones can repopulate the habitat from which the gray ones have pushed them out.
Neil and his team set live traps in Scotland's woods and estates. If they catch a red squirrel, they release it. The gray ones, however, have to die.
"There is no other option," Neil told DW. "There is nowhere for them to go, we cannot ship them back to America."
The organization trains its trappers to shoot gray squirrels with a single shot.
"Human beings have to fix it"
Even though Neil refuses to admit it, he seems to feel a little sorry for the innocent creatures.
He doesn't want to demonize gray squirrels, he says. "But the issue is this: Human beings made the problem - human beings have to fix it!" And according to Neil, the only way to fix the problem is to kill the gray squirrels. "It is a simple matter."
"Protecting your native species is essential, because they make the biodiversity of a country specific and unique," he says.
Squirrel pox danger
Every spring time, Neil takes hair samples of squirrels in certain parts of the Scottish woods to find out which kinds of squirrels live there. To get the samples, he attaches a double-sided adhesive tape to the entrance of feeder boxes filled with peanuts. Depending on the hairy results, Neil decides where to set out traps in the coming season.
The organization's latest survey showed that in 2013 the appearance of gray squirrels had dropped, compared to 2011. At the same time, red squirrels had reached into areas where they hadn't been before. "So we think our strategy is working," Neil says.
But the situation could worsen dramatically if the squirrel pox virus reaches Scotland. Gray squirrels may carry this virus, but it doesn't harm them. It is, however, lethal for red squirrels. Up to now, the virus hasn't crossed over from England to Scotland. "But we don't want to be complacent about it," Neil says. "We test for squirrel pox on a fairly regular basis - just in case."
Gray squirrels are more delicious
Humans are not the only ones hunting gray squirrels. European pine martens favor them as a meal. These weasel-like carnivores were once widespread on the British Isles, but have become extinct in many parts due to persecution. In Scotland and Ireland the population is now recovering.
For many years, conservationists have speculated that pine martens could have an effect on the numbers of red and gray squirrels. The carnivores also feed on red squirrels, but seem to prefer the bigger gray ones.
In a recent study, Emma Sheehy and Colin Lawton of the National University of Ireland in Galway confirm this theory. They found that in parts of Ireland where pine martens are frequent, red squirrels thrive whereas gray squirrels are rare.
"European pine marten abundance may be a critical factor in the American gray squirrel's success or failure as an invasive species," Sheehy and Lawton write in "Biodiversity and Conservation".
Gray squirrels are not the only introduced species that worries British conservationists. In the beginning of the 20th century, the North American mink was imported to the UK and bred for its fur. It escaped from captivity and has spread throughout most of the British Isles. Other invasive species are signal crayfish and zebra mussels. These species, too, are being hunted and eradicated.
Back at the bed and breakfast, Laura MacPherson says she supports the work of conservationists like Ken Neil - but she herself doesn't want to harm gray squirrels. Even if they do not belong to Scotland, "they are very cute", she says. "My Australian guests especially enjoy them because they don't have any squirrels in Australia, red or gray. So I like them, too."
But for the gray squrrels, being cute is not enough to make them a welcome part of the UK's ecosystems.