Are feral dogs and cats not, though? I.e., we accept the risk of pet cats and dogs escaping into the wild and reproducing, and they are quite savage hunters when they need to be (cats, IIRC, even kill just for sport).
Not to the same extent, it seems - although probably that's because people have been drilled into neutering their pets for decades. Some places do have feral dog problems. The Scottish Wildcat is also threatened by interbreeding with domestic cats - an unusual form of extinction where it simply becomes indistinguishable as a species.
