Even if there were no public health concerns or wildlife predation issues, no study supports the notion that TVNR will work in a large land mass area like Hillsborough County. In fact, no studies show any positive results in reduction of numbers and those few studies that indicate some result are ambiguous. All known studies will be listed below, including the studies most often cited by proponents of TNR. Most of those studies, when examined, do not support TNR and are badly misquoted by TNR proponents.
Critical Assessment of Claims Regarding Management of Feral Cats by Trap–Neuter–Return. Conservation Biology (2009).
This paper evaluates the TNR claims including those of effectiveness at reducing the population. As the authors note, “Mathematical models of feral cat populations indicate that 71–94% of a population must be neutered for the population to decline, assuming there is no immigration (Andersen et al. 2004; Foley et al. 2005). This level of neutering and exclusion of additional cats has not been consistently documented in practice.” They continue by observing, “Assertions of colony declines often are supported only by reference to Web sites, even in peer-reviewed articles (Gibson et al. 2002).”
Read the paper here: TNR assessment of claims
Analysis of the impact of trap-neuter-return programs on populations of feral cats. JAVMA (2005)
Here we see a very substantial two county study (Alachua County, Florida and San Diego County, California) in which the authors, including Dr. Julie Levy, a noted TNR advocate, write, “In both counties, results of analyses did not indicate a consistent reduction in per capita growth, the population multiplier, or the proportion of female cats that were pregnant.” The reality is TNR doesn’t reduce the population of feral cats.
Read the paper: JAVMA – Two County Analysis 2005
Effects of sterilization on movements of feral cats at a wildland–urban interface. Journal of Mammology (2010)
Here we see that the conclusion is “The influx of subsidized cats to natural habitats, combined with their high vagility and low trappability, makes TNR an unlikely solution for controlling feral cats on a large, rugged island like Catalina and, more generally, in other locations where human populations abut ecologically sensitive areas.”
Read the paper here: TNR 2010 Catalina Study
An Evaluation of Feral Cat Management Options Using a Decision Analysis Network. Journal of Ecology and Society (2010).
This paper demonstrates the ineffectiveness of TVNR, and shows that contrary to advocates claim, TVNR is the most expensive alternative that currently exists for management of feral cats.
Read the paper here: Ecology and Society 2010
Implementation of a Feral Cat Program on a University Campus, Texas. Journal of Applied Animal Welfare Science (2002).
This is one of the papers that advocates will cite as ‘proof’ that TNR works to reduce population numbers. However, this paper actually DOES NOT ADDRESS THE QUESTION! The key paragraph is found in the discussion, in which the authors note, “Ideally, a population estimate, using the mark-recapture method, would have been performed prior to the program’s implementation…Given this limitation and the potential difficulty in recapturing cats, and because the program’s goal was to neuter as many cats as possible, an initial population estimate was not performed. It cannot be stated definitively that the total number of cats on campus has decreased because the study was not designed to determine this.” Plus, this study is based on a very small sample group, and a very short time frame; thus it has no real value for the purpose of determining if TNR actually reduces populations.
Read the paper here: U Texas Study 2002
Effects of Implementing a Feral Cat Program in a Florida County Animal Control Service, Journal of Applied Animal Welfare Science (2002).
This is another paper relied upon by TNR advocates, but a thorough read will show the paper does not establish TNR works to reduce numbers. In fact, all the author could state in summary is, “Evaluating the effect of the implementation of the feral cat neutering program is challenging in the face of other changes within the agency and the area. Given that a number of other animal control programs and regulatory changes were implemented during the study period, separating out the effects of a single program may be impossible…Data were not collected on how many adoptable versus nonadoptable cats were impounded, so it was not possible specifically to assess changes in outcomes for feral cats, only changes in overall cat outcomes…it can be stated that the implementation of sterilization of feral cats as part of a TNR program did not result in negative changes. Although the number of impounded cats has not decreased, this may reflect in part a change in the county code in September 1995.”
Read the paper here: Orange County Fla Animal Services Study 2002
