In the late 1980s and early 1990s, some Canadian farmers imported wild boars from Europe to raise for meat. But as wild boars are wont to do, some of them escaped, either digging under fences or barreling through them. Others were set free once the boar meat market cooled.

At first, it didn’t seem like a big problem; many thought they couldn’t survive Canada’s long winters. But the boars proved hardier than some researchers expected, and now they’re causing havoc across wide swaths of Canada.

The descendants of these wild boars have interbred with domestic pigs to varying degrees, and are now found throughout western and central Canada, from British Columbia to Manitoba and beyond. As they spread, they sow environmental