“If the neuter & return is effective I'm all for it, but do they really know whether it controls the population as well as an eradication program?”
It’s sometimes argued that TNR (which means trap, sterilize, vaccinate, identify, return to original environs [with some kittens, wherever possible, going to shelters and adopted out] with long-term management and monitoring of the feral cat colony) can be successful, as good as an eradication program (when such is done properly) and even better. Success depends on building the infrastructure for an effective TNR model(s) used within that community. That infrastructure includes the willingness of private, charitable and tax-supported animal establishments (like cat welfare orgs, humane societies, veterinarian training institutions and clinics, animal control, etc.) to promote TNR and incorporate TNR services (e.g., provide live traps, conduct high-volume/low or free spay/neuter surgeries and permanent identification, provision of education on safe trapping, pre- and post- trap/surgery care, etc.) in their mission objectives. It also includes a very strong community volunteer base that knows how to safely trap, and then provide long-term management and monitoring (feeding, tidying up environs, and providing data on numbers, age, health, etc.) of feral cat colonies. It also requires a definition of animal ownership that includes the feral cat. I’m not sure if all states and municipalities are the same, but it seems that for some places where such cats are residing and tolerated, especially fed or used for rodent control, on property they are owned by the landholder or manager, who can decide, together with other direct stakeholders (e.g., renters, neighbors, etc., affected by cat behavior), how to deal with the cats.
Eradication (trap and kill) can be the better option (e.g., when habitat and/or bird species are at risk from cat behavior – I don’t find any studies that show feral cats threaten bird populations) and most effective when done properly and thoroughly. One argument against eradication is what pro-TNR folks call “the vacuum effect.” That is, there are always going to be some cats that will evade capture. Those that survive the eradication effort will breed back up to the carrying capacity of that vicinity. Or, because cats establish territories based on food availability and shelter, when managing to remove most of the cats, or even if the site’s entire cat colony is removed, other feral cats, newly abandoned/born and cats from other colonies, will move in to take advantage of food and shelter sources. So, instead of reducing cat numbers, trap and kill schemes, it’s argued, simply make room for new cats to move in and begin the breeding process all over again. Which, in turn, means that another full-scale trap-and-kill scheme will be required. And the cycle begins again.
While eradication-only schemes do provide immediate lowering of feral cat numbers, it is often only temporary, because survivors of the scheme breed prolifically to quickly re-stock and outside cats move in to form a new colony. TNR, with proper long-term management and monitoring, on the other hand, it is argued, inevitably reduces the numbers on a consistent basis because its focus is on breaking the reproductive cycle by eliminating cat reproductive capacity.
“It [TNR] sounds economically prohibitive, so I'd be concerned that it wouldn't be carried through. And it wouldn't take a whole lot of overlooked ferals to rebuild the colony.”
Eradication can also be economically prohibitive, for it requires considerable resources in terms of funds for equipment, training and staff. There are always going to be people who will lose or abandon unfixed cats, in spite of education on the importance of fixing, identifying and not abandoning cats. But also because of the alleged “vacuum effect” – if this is true - one shall require indefinitely ongoing trap-and-kill programs. Over time, such elimination-only schemes will become expensive.
For an effective TNR program one needs to build the infrastructure for such. TNR may not be so economically prohibitive in the long run, because so much of it is done by committed volunteers and charities and/or clinics that provide low-cost high-volume surgeries. Existing TNR programs are usually run by volunteers at no or very little cost. I do not have the figures, but it is alleged by Alley Cat Allies that the cost of sterilizing and returning a feral cat is less than half the cost of trapping, holding, killing, and disposing of a feral cat. At the beginning, the use of TNR on a cat colony will be expensive, more than trap-and-kill. After that, most maintenance is done by volunteers, with fewer born kittens (some that can be taken in for socialization and adoption), a few survivors of the initial TNR campaign and fewer new cats joining the colony that will require de-sexing.
Sources:
Alley Cat Allies is a great resource for volunteer feral cat caregivers, veterinarians, animal control, shelters, and anyone who has a cat colony and is interested in TNR models, how to safely trap, traps and equipment available and cost, guidelines for veterinarians who treat feral cats, legal liabilities, and more. http://www.alleycat.org/
C.A.T.S., Inc., on humane cat management and the issue of population vacuum http://www.catassist.org.au/humane.html
The American Cat Project, for definitions of “feral” cat and ownership definitions, and more http://www.americancat.net/feralproblem.html
