Um... I believe "well within the law" does not equate to being perfectly fine with shooting a cat. Honestly, I don't know if it's legal or not, but a person shooting your roaming cat is the LEAST of your worries. ("your" being used in a general sense) Cars, dogs, disease, wildlife, other cats, etc, are of far more eminence.
I absolutely notice when I see a cat that isn't a "regular". And if they allow me to approach them, I check for a collar and tags and call their owner if they have any. But, I KNOW all of the outdoor cats. I know them because I have to check my backyard for cats before I let my dogs out - and there is almost always at least one. I completely empathize with lost cats, as my favorite cat ever was stolen/lost.
Bookmarks