TNR: The Cat-alyst for Change

Trap–Neuter–Return (TNR) is one of the most humane and effective ways communities manage outdoor cats, and there’s plenty of research to back that up. TNR involves trapping community cats, having them spayed or neutered, vaccinated, ear-tipped for identification, and then returning them to the outdoor homes they know. People often wonder how well TNR works, and thankfully, we have decades of university-level studies and veterinary research that clearly show its benefits.

One of the most widely cited long-term studies took place at the University of Central Florida (UCF) in Orlando. Led by Dr. Julie Levy, researchers managed the campus’s free-roaming cat population over 11 years through TNR and adoption. The results were remarkable: the population dropped by 66%, and no kittens were born on campus after the early years of the program. This study is often referenced because it demonstrated, in a real and open environment, how sustained TNR can lead to significant population declines. A similar long-running program at the University of New South Wales (UNSW) in Sydney, Australia, produced even more dramatic results. Researchers Danielle Spehar and Peter Wolf reviewed nearly three decades of TNR efforts and found an 85% reduction in the community-cat population, with only 5% of the original cats remaining by 2019. These programs show that when TNR is consistent and well-monitored, cat populations steadily shrink.

TNR also has a major impact on local shelters. A large, targeted TNR study in Alachua County, Florida—led by Dr. Julie Levy at the University of Florida—looked at how sterilizing 2,366 cats across key neighborhoods affected shelter metrics. The findings were striking: the neighborhoods that received targeted TNR saw shelter intake rates that were 3.5 times lower than similar areas without TNR, and euthanasia rates were 17.5 times lower. This study demonstrates that TNR doesn’t just help the cats living outdoors—it directly eases the burden on shelters, especially during peak kitten seasons when resources are stretched thin.

The welfare of the cats themselves also improves significantly through TNR. Many TNR programs include vaccinations such as rabies, supported by research from the University of Florida’s Shelter Medicine Program showing reduced disease spread and improved overall health when vaccines are incorporated. Additionally, sterilized cats tend to roam less, fight less, and generally live calmer, healthier lives. Veterinary literature consistently reports better body condition, fewer injuries, and a reduction in behaviors that can lead to conflict with both other cats and nearby residents. This means TNR benefits not just the cats, but also the communities they live in.

Of course, TNR isn’t magic—it works best when certain conditions are met. Studies from researchers at Tel Aviv University emphasize that TNR is most effective when a large percentage of cats in a colony are sterilized—ideally 60% to 70% or more—and when the program is maintained over time. If new, unsterilized cats enter the area frequently due to abandonment or immigration from nearby colonies, the results can be slower. These findings help explain why small-scale or one-time TNR efforts don’t show the same dramatic results as the larger university and community programs that maintain ongoing, high-volume participation.

Veterinary organizations and shelter medicine experts overwhelmingly support TNR as a

core component of community-cat management. The Association of Shelter Veterinarians (ASV), ASPCA, and shelter-medicine teams at universities like the University of Florida and UC Davis all recognize TNR as effective and humane when combined with vaccination, community education, adoption of friendly cats, and ongoing monitoring. These endorsements reflect both scientific evidence and real-world success across shelters and neighborhoods.

Taken together, the research paints a clear and encouraging picture: TNR works. Across multiple universities and communities, TNR has led to large declines in cat populations, fewer kittens being born outdoors, lower shelter intake and euthanasia, healthier cats, and better harmony between people and the animals who share their neighborhoods. It’s a long-term, compassionate solution backed by science, and one that continues to make a meaningful difference wherever it’s applied.

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Works Cited

1. Hughes, Kathy, and Margaret R. Slater. “Trap‑Neuter‑Return at Texas A&M University Effectively Stabilizes Feral Cat Colonies.” Journal of Applied Animal Welfare Science, vol. 5, no. 3, 2002. (Paws Pets)

   
   

2. Jones, A., and C. Downs. “Managing Feral Cats on a University’s Campuses: How Many Are There and Is Sterilization Having an Effect?” Journal of Applied Animal Welfare Science, vol. 14, no. 4, 2011, pp. 304–320. (Alley Cat Allies)

   
   

3. Levy, Julie K., Diane 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, vol. 222, no. 1, 2003, pp. 42–46. (PubMed)

   
   

4. Levy, Julie K., N. M. Isaza, and Karen C. Scott. “Effect of High-Impact Targeted Trap-Neuter-Return and Adoption of Community Cats on Cat Intake to a Shelter.” The Veterinary Journal, vol. 201, 2014. (PubMed)

   
   

5. Natoli, Eugenia, et al. “Management of Feral Domestic Cats in the Urban Environment of Rome (Italy).” Preventive Veterinary Medicine, vol. 77, 2006, pp. 180–185. (Ireland's TNR Manual)

   
   

6. Neville, P. F., and J. Remfry. “Effect of Neutering on Two Groups of Feral Cats.” The Veterinary Record, vol. 114, 1984, pp. 447–450. (Ireland's TNR Manual)

   
   

7. 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, vol. 5, no. 3, 2002, pp. 203–213. (Ireland's TNR Manual)

   
   

8. “WEC423/UW468: How Effective and Humane Is Trap-Neuter-Release (TNR) for Feral Cats?” University of Florida IFAS Extension, 2015. (Ask IFAS - Powered by EDIS)

   
   

9. “Trap‑Neuter‑Return Research Compendium.” Alley Cat Allies, 2024. (Alley Cat Allies)

   
   

10. Matos, Silva, et al. “Evaluation of Population Management Based on Trap–Neuter–Return and Trap–Neuter–Adoption Practices in a Free‑Roaming Cat Colony in the Federal District, Brazil.” Animals, vol. 14, no. 17, 2024. (MDPI)

    
    

11. Kreisler, R. M., et al. (as discussed in the Frontiers editorial) — included in “Sustaining Innovation in Compassionate Free-Roaming Cat Management Across the Globe: A Decadal Reappraisal of the Practice and Promise of Trap-Neuter-Vaccinate-Return (TNVR).” Frontiers in Veterinary Science, vol. 6, 2019. (Frontiers)

    
    

12. Hamilton, Francis. “Implementing Nonlethal Solutions for Free-Roaming Cat Management in a County in the Southeastern United States.” Frontiers in Veterinary Science, vol. 6, 2019: 259. (Alley Cat Allies)