Did these things have Natural predators of some kind? Like, did some Dinosaurs or packhunting mammals like Wolves, Dire or otherwise; or a coalition of Smilos or something; manage to figure out how to hunt down Copycats? Because, there’s got to be at least something out there that’s must’ve found a way to take 'em.
Heck, I could even see large Pterosaurs like the Quetz employing it’s sharp beak to stab at it safely from the air, or even smaller ones making passing bites at them to whittle them down.