Available scientific literature presents conflicting conclusions regarding trap-neuter-return (TNR) programs, with some studies indicating population reductions in managed colonies while other literature argues that TNR is ineffective or counterproductive.
Abstract
Objective—To evaluate the effect of a long-term trapneuter-return program, with adoption whenever possible,
on the dynamics of a free-roaming cat population.
Design—Observational epidemiologic study.
Animals—155 unowned free-roaming cats.
Procedures—Free-roaming cats residing on a university
campus were trapped, neutered, and returned to
the environment or adopted over an 11-year period.
Results—During the observation period (January
1991 to April 2002), 75% of the cats were feral, and
25% were socialized. Kittens comprised 56% of the
original population. Male cats were slightly more
numerous (55%) than females. At the conclusion of
the observation period, 47% of the cats had been
removed for adoption, 15% remained on site, 15%
had disappeared, 11% were euthanatized, 6% had
died, and 6% had moved to the surrounding wooded
environment. Trapping began in 1991; however, a
complete census of cats was not completed until
1996, at which time 68 cats resided on site. At completion
of the study in 2002, the population had
decreased by 66%, from 68 to 23 cats (of which 22
were feral). No kittens were observed on site after
1995, but additional stray or abandoned cats continued
to become resident. New arrivals were neutered
or adopted before they could reproduce.
Conclusions and Clinical Relevance—A comprehensive
long-term program of neutering followed by
adoption or return to the resident colony can result in
reduction of free-roaming cat populations in urban
areas. (J Am Vet Med Assoc 2003;222:42–46)
OBJECTIVE: To predict effectiveness of 3 interventional methods of population control for feral cat colonies. DESIGN: Population model. SAMPLE: Estimates of vital data for feral cats. PROCEDURES: Data were gathered from the literature regarding the demography and mating behavior of feral cats. An individual-based stochastic simulation model was developed to evaluate the effectiveness of trap-neuter-release (TNR), lethal control, and trap-vasectomy-hysterectomy-release (TVHR) in decreasing the size of feral cat populations. RESULTS: TVHR outperformed both TNR and lethal control at all annual capture probabilities between 10% and 90%. Unless > 57% of cats were captured and neutered annually by TNR or removed by lethal control, there was minimal effect on population size. In contrast, with an annual capture rate of ≥ 35%, TVHR caused population size to decrease. An annual capture rate of 57% eliminated the modeled population in 4,000 days by use of TVHR, whereas > 82% was required for both TNR and lethal control. When the effect of fraction of adult cats neutered on kitten and young juvenile survival rate was included in the analysis, TNR performed progressively worse and could be counterproductive, such that population size increased, compared with no intervention at all. CONCLUSIONS AND CLINICAL RELEVANCE: TVHR should be preferred over TNR for management of feral cats if decrease in population size is the goal. This model allowed for many factors related to the trapping program and cats to be varied and should be useful for determining the financial and person-effort commitments required to have a desired effect on a given feral cat population.
Trap, neuter and return (TNR) describes a non-lethal approach to the control of urban stray cat populations. Currently, in Australia, lethal control is common, with over 85% of cats entering some municipal pounds euthanized. No research has been published describing TNR activities in Australia. Adults involved with TNR in Australia were invited to participate. Data from 53 respondents were collected via an anonymous online questionnaire. Most respondents were females 36 to 65 years of age, and slightly more participated in TNR as individuals than as part of an organization. Respondents generally self-funded at least some of their TNR activities. The median number of colonies per respondent was 1.5 (range 1 to over 100). Median colony size declined from 11.5 to 6.5 cats under TNR over a median of 2.2 years, and the median percent reduction was 31%; this was achieved by rehoming cats and kittens and reducing reproduction. A median of 69% of cats in each colony were desexed at the time of reporting. Most respondents fed cats once or twice daily, and at least 28% of respondents microchipped cats. Prophylactic healthcare was provided to adult cats and kittens, commonly for intestinal parasites (at least 49%), and fleas (at least 46%); vaccinations were less common. Time-consuming activities for respondents were feeding (median 4 h/week) and locating resources (median 1.1 h/week). These findings indicate that TNR, when involving high desexing rates within colonies, adoption of kittens and friendly adults, and ongoing oversight by volunteer caretakers, can reduce cat numbers over time, improve health and welfare of cats and kittens, and is largely funded by private individuals and organizations.
In August 2008, the University of New South Wales (UNSW) in Sydney, Australia, commenced a trap-neuter-return (TNR) program to manage the population of approximately 69 free-roaming unowned urban cats on its Kensington campus. The goals of the program included an ongoing audit of cats on campus, stabilization of cat numbers through TNR, and a subsequent reduction in cat numbers over time while maintaining the health of remaining campus cats. Continuation of the TNR program over nine years resulted in a current population, as of September 2017, of 15 cats, all desexed (78% reduction). Regular monitoring of the cats through a daily feeding program identified a further 34 cats that immigrated on to campus since initiation of the program; these comprised 28 adult cats (16 unsocialized, 12 socialized) and six solitary kittens. In addition, 19 kittens were born on campus, 14 of which were born to immigrant pregnant females. Unsocialized adult immigrants were absorbed into the resident campus population. Where possible, socialized adult immigrants, solitary kittens, and campus-born kittens were removed from campus through rehoming. Overall, reasons for reductions in the cat population (original residents, immigrants, campus-born kittens; n = 122) included rehoming or return to owner (30%), death/euthanasia (30%) and disappearance (29%). This successful animal management program received some initial funding from the university to support desexing, but was subsequently funded through donations, and continues with the university's approval and support.
Simple Summary Since the early 1990s, the use of trap-neuter-return (TNR) as a humane alternative to the lethal management of stray and feral cats (also known as community cats) has expanded in the United States. Over this time, numerous studies have pointed to the effectiveness of TNR at reducing community cat numbers, although many of these investigations have covered relatively short time periods (3 years or less). A seminal paper by Levy et al. in 2003, documented a significant decline in community cat numbers on the campus of the University of Central Florida (UCF) over a 11-year period. Since 2017, a series of peer-reviewed articles have described other examples of long-term reductions in community cat numbers associated with TNR. The present study adds to this growing body of evidence by revealing the extent to which the results first reported by Levy et al. have been sustained over a subsequent 17-year period. After a total of 28 years, 10 (5%) of 204 total cats enrolled in the UCF TNR program, remain on campus and the campus community cat population has declined by 85% from the completion of an initial census in 1996 to 2019. Abstract A growing body of evidence indicates that trap-neuter-return (TNR) is not only effective at reducing community cat numbers, but that such reductions are sustainable over extended periods. Recently, a series of peer-reviewed articles documenting long-term declines in community cat populations associated with TNR have been published. The present study adds to this pool of evidence by updating and reexamining results reported from the campus of the University of Central Florida (UCF) in 2003 by Levy et al. From 1991 to 2019, a total of 204 cats were enrolled in a volunteer-run TNR program on the university grounds; 10 cats (5%) remained on site at the conclusion of the present study. The campus community cat population declined by 85% between 1996, the year an initial census (indicating the presence of 68 cats) was completed, and 2019. In addition, 11 of 16 total colonies were eliminated over a 28-year period. These results occurred despite significant growth in enrollment at UCF over the same time frame, which suggests that with sufficient ongoing management of colony sites, declines in community cat populations associated with TNR are sustainable over long periods and under varying conditions.
Trap-Neuter-Return (TNR) programs, in which stray cats are captured, neutered and returned to the environment are advocated as a humane, ethical alternative to euthanasia. We review the TNR literature in light of current debate over whether or not there should be further TNR trials in Australia. We revisit the problems arising from stray cats living in association with human habitation and estimate how many stray cats would have to be processed through a scientifically-guided TNR program to avoid high euthanasia rates. We also identify 10 ethical and welfare challenges that have to be addressed: we consider the quality of life for stray cats, where they would live, whether the TNR process itself is stressful, whether TNR cats are vulnerable to injury, parasites and disease, can be medically treated, stray cats’ body condition and diet, and their impacts on people, pet cats, and urban wildlife, especially endemic fauna. We conclude that TNR is unsuitable for Australia in almost all situations because it is unlikely to resolve problems caused by stray cats or meet ethical and welfare challenges. Targeted adoption, early-age desexing, community education initiatives and responsible pet ownership have greater promise to minimize euthanasia, reduce numbers rapidly, and address the identified issues.
As of 2002, estimates of free-roaming domestic cat (Felis catus) populations exceeded 100 million individuals, throughout the United States. Many lost or abandoned cats will revert to living outdoors as free-roaming individuals. To try to control the abundance of free-roaming cats, trap-neuter-release (TNR) programs have been implemented across the United States. The goal of many TNR programs is to reduce cat populations by sterilizing the individuals to prevent breeding, while also providing food and water to the unconfined colony. However, wildlife conservationists question the effectiveness of TNR programs. The objectives of my study were to: determine the population size and apparent survival of free-roaming cats in areas managed by a TNR program, determine population size and apparent survival of free-roaming cats in areas not managed by a TNR program, and compare the population sizes of TNR managed populations to those of unmanaged cat populations. Between September 2011 and September 2012, free-roaming cats were trapped and marked at two sites managed by a TNR program, and at two unmanaged sites. Population estimates indicated seasonal population changes in the unmanaged sites as well as TNR site 1, but not TNR site 2. TNR site 1 had a lower proportion of neuter cats ( < 50% neutered) while TNR site 2 had a much higher proportion of neutered individuals (~90% neutered). Population estimates of the unmanaged sites and TNR site 1 increased in the spring and decreased through the winter months. Population estimates for TNR site 2 remained constant throughout the year. This study showed TNR programs will need to maintain a high proportion of neutered individuals to prevent population increases and that a highly neutered colony is managed for a seasonally stable population of cats as opposed to a decreasing population.
Trap–neuter–return (TNR), also known as trap–neuter–release, is a controversial method that attempts to manage populations of feral cats. The process involves
Trap–neuter–return (TNR), also known as trap–neuter–release, is a controversial method that attempts to manage populations of feral cats. The process involves live-trapping the cats, having them neutered, ear-tipped for identification, and, if possible, vaccinated, then releasing them back into the outdoors. If the location is deemed unsafe or otherwise inappropriate, the cats may be relocated to
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The Australian Academy of Science: "reviews across many studies show that TNR is not effective: it does not minimise cat populations, it does not stop cats from killing wildlife, and it encourages people to dump unwanted cats."
The National Wildlife Federation: "As a wildlife conservation organization, the National Wildlife Federation doesn’t support Trap, Neuter, Release/Return programs simply because they don’t work to minimize the negative impact of feral cats on wildlife populations. Feral cats are primarily responsible for the 1.3-4 billion birds and 6.3–22.3 billion mammals killed annually by domesticated cats in the United States and perpetuating feral cat colonies is incompatible with sound, science-based wildlife conservation."
PETA does not endorse TNR, citing research finding it is not an effective intervention, along with data finding short life expectancies and inhumane living conditions for feral cats. They think that "You can’t be an animal advocate and support trap-neuter-release. It’s not about you. TNR makes humans, not cats—and certainly not wildlife—feel better, convincing themselves that they’re doing good. If you care about animals, you can’t logically support leaving cats outdoors to roam or dumping them on the streets through trap-neuter-release programs. Life on the streets is no life at all for cats—and for the wildlife they hurt and kill, it’s a death sentence."
The Wildlife Society opposes TNR programs because it "undermines the work of wildlife professionals and severely jeopardizes the integrity of native biodiversity."
American Bird Conservancy opposes TNR programs: "Unfortunately, TNR programs have been shown to fail to reduce feral cat populations while simultaneously maintaining feral cats on the landscape, where they contribute to wildlife and public health risks. [...] Scientific evidence regarding TNR clearly indicates that TNR programs are not an effective tool to reduce feral cat populations. Rather than slowly disappearing, studies have shown that feral cat colonies persist and may actually increase in size"
In a review of TNR programs, RSPCA Australia concluded that "as a long term strategy, in most of Australia, TNR is…
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