TNR - Trap, Neuter, Release - common program in many communities now, as more cats roam for longer periods and become permanently feral <in U.S.> than dogs do, for a variety of reasons. TNR part of feral cat colonies care-taking programs, often where there will be a group of people, either volunteers from a shelter or feral cat rescue, or just themselves as volunteers - who monitor and feed cat colonies. TNR can be considered more humane than actually trying to trap and re-home the cats, as adult ferals are often un-manageable in a human household and really don't do well.