American Squirrels are Conquering Europe, and It’s Bad

If you live in the eastern United States, you’re probably familiar with the ubiquitous eastern gray squirrel. Cute, derpy, annoying…whatever term you have for them, they are crucial to North American ecosystems, spreading seeds and fungal spores where they can grow and flourish. However, outside of North America, gray squirrels are waging a war against their European counterpart, the red squirrel, and the gray squirrels are winning.

But this war is not conventional warfare, where these fluffy tailed rodents engage in hand to hand combat. No. This is more like economic warfare, where every acorn is as precious as dollars and Euros. Despite the lack of bloodshed, this war is just as deadly.

Within 15 years of gray squirrels entering red squirrel habitat, red squirrels go extinct. I mean, just look at this map of gray squirrel population expansion in the UK and Ireland between 1945 and 2010. The numbers aren’t looking good for red squirrels in the British Isles.

Map of red and gray squirrel populations in the UK from 1945 to 2010. Source: Red Squirrel Survival Trust

Prior to the gray squirrel invasion, there were over 3.5 million red squirrels in the UK. Today, there are over 2.5 million gray squirrels and less than 140,000 red squirrels in the UK. 85% of the remaining British red squirrels are in Scotland.

So why do these American squirrels fare better than their European counterparts? Is it because American squirrels have a huge military and millions of guns? No, that’s not it.

Like many invasive species, eastern gray squirrels are foreigners who have few natural predators or parasites in Europe. Only the pine marten has been known to prey upon them, and it’s the reason gray squirrels have been kept at bay in Ireland and Scotland.

Another reason gray squirrels are dominating red squirrels is their physique. Some studies have suggested that gray squirrels are more fit than red squirrels and can breed better under stress. They can also better digest the proteins and fats in acorns than red squirrels. It’s a weird flex, but the red squirrels aren’t laughing.

Gray squirrels also carry a disease called squirrel parapoxvirus, which does not affect them but is often fatal for red squirrels. Formby, England experienced an 80% decline in red squirrel populations due to the parapoxvirus.

In better news, mainland Europe is faring better against these American invaders. Only Italy is grappling with gray squirrels at the moment, although things could change if they cross the Alps and expand into France and Switzerland over the next few decades. We can only assume that the allure of French cuisine and skiing in the Swiss Alps is far too great for these radical rodents to resist.

What’s crazy is that the eastern gray squirrel has not limited its invasion to Europe. Countries as far flung as South Africa and Australia have experienced their own Squirrel War Three. Thankfully, the squirrels have been unable to spread beyond the Western Cape in South Africa and were eradicated from Australia in 1973.

Even on their native North American continent, gray squirrels are spreading outside their native range. These east coast fuzzballs are appearing more and more on the west coast, from Central California all the way up to southwest British Columbia. Now, they have become the most commonly sighted squirrel species in west coast cities and suburbs, displacing native west coast squirrels, such as the American red squirrel.

However, before you start blaming the squirrels for all this carnage, the vast majority of these squirrels were introduced by humans intentionally. People released them in parks around the world to, presumably, add some cuteness to the environment. Like many disastrous environmental hiccups, we are directly responsible for problems and solutions.

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