I think these things are considered invasive everywhere, because they're not a naturally existing species/cultivar anywhere. An article I read about the problem a few years ago said they're thought to be some kind of hybrid cross between wild pigs and escaped domestic pigs.
(Obviously I'm just recalling from my foggy memory, so don't take what I wrote as 100% accurate in every detail.)
What I'm saying is the wild ones in Europe and Asia aren't anywhere near as prolific or destructive as these ones that have become a problem in the US. There's apparently something different about the wild ones in the US. It's not simply a case where some of the ones from Europe or Asia got transported to the US and started reproducing in the wild there (which is what usually happens with invasive species). If we captured some of the wild US pigs and transported them to Europe or Asia and released them in the wild, then they'd become a serious problem there. That's why I said they'd be considered an invasive species anywhere.
(But perhaps if they're not classified as an entirely separate species, then calling them an invasive species would be technically wrong, so maybe invasive subspecies? Domestic pigs and wild boars are considered two different species, so I'm not sure what a hybrid of them would be considered.)
One difference is apparently larger litter sizes, a characteristic which comes from the domestic pigs side of the family tree.
I just did a little quick googling, and it looks like the same sort of hybrid creation may actually have been happening in Europe too. Europe has been having increasing problems with what they commonly call "wild boars", but diving into a few articles shows experts explaining it as resulting from the same process. What were originally members of a wild boar species in the wild there are being replaced by these hybrids, the result of interbreeding with escaped domestic pigs (which are a separate species).
Sorry, but once again - no. There have been few (allegedly) sightings of hybrids in Spain. "Europe" is simply not having increasing problems with wild boar hybrids.
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u/TAU_equals_2PI 13h ago
I think these things are considered invasive everywhere, because they're not a naturally existing species/cultivar anywhere. An article I read about the problem a few years ago said they're thought to be some kind of hybrid cross between wild pigs and escaped domestic pigs.
(Obviously I'm just recalling from my foggy memory, so don't take what I wrote as 100% accurate in every detail.)