Nature works against extinction.  Kill cats and they reproduce faster.  It's that simple.  Add neutered and spayed cats to the colonies and the populations slows down and eventually stops.  We can already see how great the kill policies for O`ahu's chickens has worked out.  C&C stopped the no-kill rooster control contract for a few years and the chicken population has exploded and they have spread all over the island.  But because it's really about political payoffs it provides a reason for the Hawaiian InHumane Society to get paid a lot of money to make like they are addressing the problem, and so that their boardmembers and friends of the InHumane Society can continue to write checks to Mayor Caldwell's political campaigns.