Does Trap-Neuter-Return work?
The short answer is no. Reduced rates of euthanasia at municipal or county animal shelters do not mean there are any fewer feral cats in a given area. Studies have shown that numbers of cats can increase during TNR.
Effective?
No. The American Veterinary Medical Association has stated that "…the reduction in the total number of free-roaming cats these programs will effect is insignificant."
Good for public health?
No. The National Association of State Public Health Veterinarians has stated that "There is no evidence that colony management programs will reduce diseases…"
Good for wildlife?
No. The Wildlife Society has stated that, "Even if conservative estimates of prey taken are considered, the number of prey animals killed is immense. Feeding cats does not deter them from killing wildlife…"
Good for feral cats?
No. People for the Ethical Treatment of Animals has stated, "Having witnessed firsthand the gruesome things that can happen to feral cats, we cannot in good conscience advocate trapping and releasing as a humane way to deal with overpopulation."
Good for the community?
No. Read about municipal experiences by clicking here.
Legal?
See what the US Department of the Interior has to say by clicking here.
On the website of Alley Cat Allies they state that, "Trap-Neuter-Return is the only effective and humane option for feral cats" and list what they refer to as 'Key Scientific Studies on Trap-Neuter-Return' to support this claim.
On the website of Neighborhood Cats they also show selected research in an effort to substantiate this method.
However, in fact there is little to no scientific support for the TNR method, as indicated below.
What follows are the citations of those studies and critical analyses.
From Alley Cat Allies:
Scott, Karen C., Julie K. Levy, and Shawn P. Gorman. Body Condition of Feral Cats and the Effect of Neutering. Journal of Applied Animal Welfare Science 2002, 5(3): 203-213.
Scott et al. 2002 does not measure TNR's effectiveness in eliminating colonies.
Neville, P.F. and J. Remfry. Effect of Neutering on Two Groups of Feral Cats. The Veterinary Record 1984, 114: 447-450.
Neville and Remfry 1984 does not show decrease in colony size. According to the authors, the purpose of TNR is to stabilize, not reduce, the number of cats, at a "desired level of population."
Hughes, Kathy L. and Margaret R. Slater. Implementation of a Feral Cat Management Program on a University Campus. Journal of Applied Animal Welfare Science 2002, 5(1): 15-28.
Hughes and Slater 2002 removed more than one-third of the 158 cats in a TNR program on the Texas A&M campus, but despite a high removal and trapping effort, the authors write: "It cannot be stated definitively that the total number of cats on campus decreased because the program was not designed to determine this."
Levy, Julie K., David W. Gale, and Leslie A. Gale. Evaluation of the Effect of a Long-Term Trap-Neuter-Return and Adoption Program on a Free-Roaming Cat Population. Journal of the American Veterinary Medical Association 2003, 222(1): 42-46.
Levy et al. 2003 state that "…virtually no information exists to support the contention that neutering is an effective long-term method for controlling free-roaming cat populations." They describe an 11-year study of a TNR program combined with intensive cat removal efforts on a Florida university campus. They report frequent new immigration from abandoned cats, noting that: "free-roaming cats do not appear to have sufficient territorial activity to prevent new arrivals from permanently joining colonies." They removed (via adoption and euthanasia) 58% of the total cats in order to help achieve a decline from 68 to 23 cats; 21% of the attrition was due to cats' disappearances and dispersal into the "surrounding wooded environment."
Natoli, Eugenia, et. al. Management of Feral Domestic Cats in the Urban Environment of Rome (Italy). Preventative Veterinary Medicine 2006, 77: 180-185.
Natoli et al. 2006 report results of surveys of TNR programs for cats in Rome, Italy, from 1991 to 2000, which included more than 10,000 cats. In 55 colonies numbers of cats decreased, while in 48 colonies numbers of cats increased or remained stable. A reported estimate of 21-31% decrease in numbers of cats initially present was offset by a 16-21% increase in numbers due to immigration. The authors conclude that "all these efforts without an effective education of people to control the reproduction of house cats (as a prevention for abandonment) are a waste of money, time, and energy."
From Neighborhood Cats:
Levy, Julie K., David W. Gale, and Leslie A. Gale. Evaluation of the Effect of a Long-Term Trap-Neuter-Return and Adoption Program on a Free-Roaming Cat Population. Journal of the American Veterinary Medical Association 2003, 222(1): 42-46.
See above.
Mendes-de-Almeida, F., et al. The impact of hysterectomy in an urban colony of domestic cats. International Journal of Applied Research in Veterinary Medicine 2006, 4: 134-141.
Mendes-de-Almeida, F., et al. 2006 reports on a study of a feline population control method over 36 months at the zoological garden of Rio de Janeiro. From the reported results, the program appears to have had some success in reducing cat populations, but the control method utilized was significantly different from TNR:
1. Cats were not sustained in colonies. There is no mention of deliberate provision of food, water, shelter, or any other care.
2. Contrary to how TNR is practiced, cats were sterilized by hysterectomy with conservation of gonads. Authors specifically make the point that "Historically, surgical sterilization with removal of gonads has been recommended as a form of population control of feral cats, although this lacks any scientific endorsement. On the contrary, there is evidence that sterilization with removal of gonads does not inhibit population growth." The authors stress several times that their approach to sterilization, which is different from the one utilized in TNR programs, is key to achieving population control.
3. The program was executed in a well-defined somewhat isolated targeted area (Zoo, 13.8 hectares), was well-organized and planned. For example, cats were captured using hand nets after being fed food laced with flunitrazepam. It would be very difficult for a TNR program ran in an open system to utilize similar methods.
Reece, J.F. and S.K. Chawla. Control of rabies in Jaipur, India, by the sterilization and vaccination of neighbourhood dogs. The Veterinary Record 2006, 159: 379-383.
Reece and Chawla 2006 discuss rabies control efforts in neighborhood dogs in India. If we are to compare rabies control efforts in dogs to that of cats, then why don't we begin by examining what has been done in the United States? The CDC announced in 2007 that canine rabies has been eliminated in the U.S. through the implementation of dog vaccination, licensing and stray dog control (not by subsidizing free-roaming packs of feral dogs). In the Compendium of Animal Rabies Prevention and Control, 2008, the recommendation is that, "Stray dogs, cats and ferrets should be removed from the community."
Stoskopf, M. and F. Nutter. Analyzing approaches to feral cat management - one size does not fit all. Journal of American Veterinary Medical Association 2004, 225: 1361-1364.
Stoskopf and Nutter 2004 - not peer reviewed. This paper is related to work done by Nutter for her Ph.D. thesis in which a comparison was made between colonies where cats were trapped, sterilized, returned and sustained vs. colonies where cats were sustained without being neutered. There was no comparison made to trap and remove. The conclusion was that sterilizing and feeding is better than just feeding and letting them breed. 98% sterilization rate was achieved in sterilized colonies. Even with this high rate, the mean estimated extinction time for a colony was 12.8 years, assuming that newcomers were sterilized. She concluded that, "The models suggested that [TNR]… will not lead to long-term reduction in the numbers of cats because colonies can re-establish due to immigration."
Hughes, K.L., M.R. Slater and L. Haller. The effects of implementing a feral cat spay/neuter program in a Florida county animal control service. Journal of Applied Animal Welfare Science 2002, 5: 285-298.
Hughes et al. 2002 describe 6-year study of a TNR program in a Florida county for the purpose of studying its effectiveness in reducing euthanasia rates, public complaints, and costs. There is no assessment of possible population changes in response to TNR, and thus no information about the effectiveness of TNR in reducing cat populations.
Levy, J.K. and P.C. Crawford. Humane strategies for controlling feral cat populations. Journal of American Veterinary Medical Association 2004, 225: 1354-1360.
Levy and Crawford 2004 - not peer-reviewed. The authors state that "…the extended survival of feral cats following sterilization indicates that natural attrition would result in a slow rate of population decline" and further state that, "Immigration or abandonment of new cats may occur and could substantially limit the success of TNR if an ongoing surveillance and maintenance program is not effective."
Lord, L. Attitudes toward and perceptions of free-roaming cats among individuals living in Ohio. Journal of the American Veterinary Medical Association 2008, 232: 1159-1167.
Dr. Lord's survey describes TNR as "…a program in which stray and feral (or wild) cats already living outdoors are humanely trapped, vaccinated, and spayed/neutered by veterinarians. Kittens and tame (stray) cats are adopted into good homes. Healthy adult cats too feral (wild) to be adopted are returned to their familiar habitat under a person's care."
This seems to give the impression that veterinarians are involved in trapping cats and states that kittens and tame cats are adopted into good homes, which may or may not be true. Healthy cats are returned to their familiar habitat, however unsafe or environmentally sensitive an area may be. Domestic cats are not a natural part of any North American ecosystem. Feral cats are often not tested and sometimes not vaccinated for fatal feline diseases. Being under a person's care conjures up an image that does not fit what seems to be commonplace at managed colonies (piles of food, trash, the absence of regular health care, lack of observation, and inconsistent trapping by caregivers). Nowhere is the word 'colony' even mentioned. There is a dark side to TNR, but no one would know by the description in Dr. Lord's survey.
Trap-Neuter-Return does NOT work! Solutions to the overpopulation of feral cats must not come at the expense of public health, natural resources, the cats or property rights.
For information about Public Health click here.
For the latest information on Managed Cat Colonies and TNR from the American Bird Conservancy click here.
For Examples of Responsible Cat Management click here.
Is your local or county government considering legalizing TNR? Click here.
Check out our References page for more information.