Peer-reviewed Studies of Trap-Neuter-Return (TNR)

It’s Science


TNR is the only effective method of controlling the community cat population. The following are key studies demonstrating the efficacy of TNR and its value to local governments.

TNR reduces shelter intake and euthanasia for cats. 

  • A 2016 study of eight years of data from San Jose Animal Care and Control determined that the implementation of a Shelter-Neuter-Return program reduced both cat intake and cat euthanasia.[1] Resources previously spent on cat euthanasia were reallocated to provide medical care to cats with upper respiratory infections.
  • A study of shelter data over six years in Orange County, Florida concluded that after implementing TNR, cat euthanasia decreased while the number of complaints and calls about cats to animal control also declined.[2]

TNR reduces the overall community cat population.

  • A 2002 study at Texas A&M University found a 36% reduction in the community cat population, coupled with a decrease in nuisance complaints only two years after TNR was introduced.[3]
  • An eleven year study of community cats at the University of Central Florida campus determined that the campus cat population decreased by 85% after TNR was instituted.[4]

Low-level culling (killing) of cats can increase the population.

  • A 2015 study on the island of Tasmania determined that the “low-level culling of feral cats” actually increased the cat population. Researchers found the number of feral cats increased by 75% at one site and 211% at the other site.[5]


[1] Edinboro, C, Watson, H, Fairbrother, A. (2016) “Association between a shelter-neuter-return program and cat health at a large municipal animal shelter.” Journal of the American Veterinary Medical Association 248, no.3:298-308.

[2] Hughes, Kathy L., Margaret R. Slater, and Linda Haller. “The Effects of Implementing a Feral Cat Spay/Neuter Program in a Florida County Animal Control Service.” Journal of Applied Animal Welfare Science 5 (2002): 285-289.

[3] Hughes, K.L. and Slater, M.R. (2002). Implementation of a feral cat management program on a university campus. Journal of Applied Animal Welfare Science, 5, 15-28.

[4] Levy, J.K., Gale, D.W., and Gale, L.A. (2003). 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 222, 42-46.

[5] Lazenby, B.T., Mooney, N.J. & Dicman, C.R. “Effects of low-level culling of feral cats in open populations: a case study from the forests of southern Tasmania.” Wildlife Research 41, 407–420 (2015)




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