Like other Beatrix Potter characters, Squirrel Nutkin is mischievous and downright rude. Unlike his “great many cousins,” Potter writes, Nutkin shows no respect to an owl named Old Brown and ends up losing half his tail as a result.

But Squirrel Nutkin, whose cautionary tale of impertinence (and maybe working-class rebellion) was published in 1903, nonetheless endeared generations of Brits to the reddish rodents native to their island nation. It helps that the animals are impossibly cute, with paws that look like furry little mittens and alert ears tipped with tall tufts of hair.

So it is with great alarm that residents of the United Kingdom have seen red squirrel numbers dwindle so rapidly that a partnership of conservation organizations, Red Squirrels United, now says they may become extinct within 35 years without help from humans.

The cause of the Nutkins’ woes? Invasive North American gray squirrels, the kind found in the United States. And part of the solution, according to Red Squirrels United: intensive monitoring of the native red squirrels — and trapping and killing of the immigrant grays.

“Seeing them in the wild is quite special,” Cathleen Thomas, Red Squirrels United’s program manager, said of the remaining red squirrels. Yet, she added in an interview, “where we have gray squirrels, we don’t have red squirrels very long.”

It may sound strange to think of squirrels as an invasive species, a label more commonly associated with animals like pythons and cats. But that is what the American squirrels are in England, where they were introduced in 1876 by Victorians who, Thomas said, “would travel the world and bring back interesting animals.” Environmental historian Peter A. Coates describes this time as “an era of innocent faith in the virtues of acclimatization” and writes that gray squirrels were purposely released several times between 1876 and 1929 “to enrich Britain’s impoverished fauna.”

Unfortunately, gray squirrels greatly out-competed their red counterparts, Thomas said. They appreciate the same foods — hazelnuts are a favorite — and live in the same habitat, but the grays are larger and live in bigger groups. They also spread disease to red squirrels.

“They can be quite sneaky,” Thomas said. “They watch where red squirrels bury nuts and go and dig them up and eat them.”

Today, an estimated 3.5 million gray squirrels inhabit the U.K., dwarfing the population of about 140,000 red squirrels, almost none of which remain in southern England. To help the remaining natives, Red Squirrels United is seeking 5,000 volunteers in red-squirrel strongholds to log sightings, monitor feeders and set up remote cameras to record their behavior.

Volunteers will also be asked to report the gray outlaws, and some with special training will participating in “removing” the squirrels. That’s wildlife conservation-speak for killing — not deporting — which Thomas said is typically done by “shooting and cranial concussions.”

“Lethal control is a last resort,” but an effective one, she said. “We work to very high levels of humane standards to make sure there’s no unnecessary suffering.”

The effort is the latest in a long public battle in England against the gray squirrel, a fight that has attracted the backing of Prince Charles. The prince, the Guardian recently reported, is so eager to save reds that he is supporting a plan to give gray squirrels contraceptives hidden in dabs of Nutella.

The defense of red squirrels there has taken on decidedly nationalistic tones, Coates writes, despite evidence that gray squirrels have been scapegoated as the main reason for the Nutkins’ decline, when the latter was already under pressure from disease and deforestation.

In a fascinating paper, “Over Here: American Animals in Britain,” Coates describes decades of anti-gray-squirrel arguments cloaked in locals-vs.-foreigners language. In a 2006 House of Lords debate over squirrelshe recalls, Lady Saltoun of Abernethy “observed that [red squirrels] are ‘rather like quiet, well-behaved people who do not make a nuisance or an exhibition of themselves, or commit crimes, and so do not get themselves into the papers in the vulgar way gray squirrels do.’ ”

Or, as the Guardian jokingly wrote: “Red squirrels are British. Red squirrels have a stiff upper lip. Red squirrels cry at the national anthem. Red squirrels have a fundamental understanding of decent British values. Not like these invading greys.”

Those familiar with Potter’s anthology will recall that Squirrel Nutkin was not the author’s only squirrel protagonist. The other was a gluttonous fellow named Timmy Tiptoes — and he was a bushy-tailed gray squirrel. Linda Lear, author of a biography on Potter, suggests that she wrote the book in 1911 to appeal to her American audience: It also included chipmunks and a black bear, both of which are native to the other side of the Atlantic. It’s unlikely Potter had ever seen a gray squirrel, which hadn’t yet reached the area where she lived, Lear notes.

“Because Timmy Tiptoes and Chippy Hackee [the chipmunk] are not drawn from nature, their images have a certain artificiality that her other animal characters do not have,” Lear writes. “The awkwardness of both story and image reflects how difficult it was for Potter to write about nature that was outside her knowledge or that she had not directly observed.”

What a difference a century makes. If Potter were writing today, she’d certainly have spotted many a gray squirrel in Britain’s Lake District, where the author spent holidays as a child and set “The Tale of Squirrel Nutkin.” According to maps from Red Squirrels United, that region’s squirrels were all red in 1945. Today, the maps show, they are vastly outnumbered by gray invaders.

All of which means that if Squirrel Nutkin is to survive, Timmy Tiptoes must go, red squirrel advocates say.

“It’s an unfortunate part of red squirrel conservation that we have to kill gray squirrels,” volunteer Julie Bailey, who lives in northwest England and has been trapping and shooting gray squirrels, told the Guardian. “But we have an obligation to undo the damage the Victorians did by bringing them here in the first place.”

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