Hi, as an observer, I wasn't interpreting "cats maim and kill for fun" as implying sadism, but as a sort of, cats find hunting fun the same way a kid finds playing capture the flag fun, in terms of exercise plus objectives, a sort of "yay I caught the thing!", without the cats really having any understanding of the suffering inflicted, because it's equally fun for them to play-hunt with moving toys. The maiming and killing is a consequence of them having fun outside with native wildlife and they don't know they're causing the prey pain because they're cats. But cats certainly are complex enough to experience something like pleasure, even if it's different from a human experience of it and likely simpler, and that's why indoor cats still need enrichment that lets them fulfill those behaviors--because they are capable of pleasure and boredom.
Are there any studies about the long-term effectiveness of TNR programs on cat populations on islands, where cats migrating in from nearby areas isn't really a thing?