I believe this can also be applied to the feral cat population. That even if cats are being congregated in one area by being fed to potentially be S/N it does not eliminate the fact that the population as a whole is very large and that in the mean time these critters are being fed and reproducing and that inevitably individuals will slip through.
There are some large colonies in my area that are being managed well and producing very few kittens. The majority of those kittens are trapped, socialized, and adopted out... thus not adding to the actual population of the colony. Cats that have been fixed and released are ear-tipped, so the caretakers know exactly who has and hasn't been given the snip, and it's obvious if a new, unaltered cat shows up.
With large colonies, I think it's generally customary to spay and neuter in large numbers (we have clinics that do this), so you don't end up with a massive feeding-related population boom. It probably wouldn't be a great idea to start feeding a large colony while attempting to alter one cat at a time, but if you manage to catch everyone relatively quickly, the population shouldn't increase by much.
While I'm opposed to killing ferals, and believe that TNR offers an option that (if done correctly) is both more effective and more humane... my biggest problem with the Nebraska study is the fact that they advocate the use of crush and leghold traps as being "humane" (which they aren't), and the authors go so far as to suggest that such methods are in line with the AVMA's position on feral cats (which, again, they aren't). The authors also seem to have a relatively poor understanding of TNR and its intentions.
And, having spent one (very unpleasant) year at said University, the biggest problem they have is their students. If they'd make more of an effort to crack down on all the students who are sneaking kittens in at the beginning of the year only to abandon them, intact, at the end, they wouldn't have such a problem with feral cats.
Feral cats can be an issue feces-wise, but these cats are generally petrified of humans and won't approach them. If someone is attacked by a cat, odds are, it's either a stray or a free-roaming owned cat. (We had a lovely neighbor once who, when their cat began displaying bizarre and aggressive behaviors, opened the door and gave kitty the boot. Kitty then followed me home from a babysitting job, and proceeded to maul the living daylights out of my father and I. When we finally tracked down the owners, they were like, "Uh... yeah. She started doing that two months ago. That's why we put her outside." FAIL.
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