Research| Veterinarian Awareness

As the leading experts on cats, Alley Cat Allies vigilantly monitors and reviews emerging research. In the early days of Trap-Neuter-Return (TNR), questions were raised about whether vasectomies might be more effective than neutering. This subject was explored in the 1980s and 1990s, especially in the United Kingdom, and the scientific consensus is reflected in contemporary practice: neutering is the standard.

A 2013 modeling study by Tufts University briefly resurrected the old debate about vasectomies, and also touted hysterectomies as an alternative to spaying. Once in a while, vasectomies only, vasectomies and spaying, or Trap-Vasectomy-Hysterectomy-Return (TVHR), are deliberated as potential alternatives to spaying and neutering. However, given what we know about cat biology and social behavior from decades of research, Alley Cat Allies cannot recommend vasectomies and hysterectomies, or TVHR.

What is Trap-Vasectomy-Hysterectomy-Return (TVHR)?

TVHR differs from TNR in the type of sterilization surgery performed on the cats. Unlike traditional spays (ovariohysterectomy) and neuters (castration), vasectomies and hysterectomies result in sterile but sexually active cats. Hormone-driven mating continues, and the cats maintain the behaviors of intact cats that often lead to calls to municipalities and animal control. This includes territorial fighting, marking territory, yowling, and moving in a larger range of territory.

A 2013 Tufts University modeling study claims that TVHR causes a more rapid stabilization and decline in feral cat populations than TNR.1 However, there were many problems with this study that undermine its claims. First, it wasn’t a study of actual community cats in real-world scenarios—the researchers based their findings entirely on a computer simulation model. For example, the modeling did not take into account kittens who are adopted in TNR programs in their statistical modeling of TNR’s effectiveness. The authors of the Tufts University study even admit that stressful mating behaviors continue after TVHR, but not with TNR.

Is TVHR a good way to stabilize community cat populations?

Alley Cat Allies does not recommend TVHR, for several reasons:

  • TVHR disregards cats’ quality of life by allowing the continuation of stressful mating behaviors, like fighting.
  • TVHR fails to address nuisance behaviors associated with mating, and therefore does not help the cats coexist with their human neighbors.2
  • Support for TVHR is based on assumptions that are not supported by current understanding of cat biology and social behavior.3
  • Unlike TVHR, TNR has been applied in the field for decades and is proven to be effective in real-world settings, not just computer models.4
  • Vasectomized male cats show no advantage over neutered males in stabilizing colony populations, vasectomized male cats continue to roam, and vasectomies are a more time-consuming, difficult, and expensive procedure than neutering.5
  • Trap-Neuter-Return (TNR) is more effective in population control and colony members are more stable.5

Our goal, and the goal of every TNR program, is to do what is best for the cats—stabilizing colony size is just one reason why TNR is so effective and popular. The myriad health and community relations benefits of spayed and neutered cats are only achieved through TNR, not through TVHR.  At this time, there is no new product or approach that provides as many benefits and improves the lives of cats as comprehensively as TNR does.

What is the best surgical procedure for sterilizing community cats?

Trap-Neuter-Return remains the Best Practice and is the recommended standard for community cat care, offering the most benefits to both cats and the community. TNR stabilizes populations, improves the health of individual cats as well as the colony as a whole, and greatly increases harmony so cats and people can co-exist.(7)(8) Spay and neuter surgeries sterilize and end mating behaviors that are stressful to cats and frequently the cause of calls to local government animal control agencies. TNR remains the only humane and effective approach to community cats.

Alley Cat Allies will only endorse advancements that ensure health and safety for all cats. You can count on us to keep you updated.


[1] McCarthy, R.J., S.H. Levine, and J.M. Reed, Estimation of effectiveness of three methods of feral cat population control by use of a simulation model. Journal of the American Veterinary Medical Association, 2013. 243(4): p. 502–511. http://dx.doi.org/10.2460/javma.243.4.502
[2] Nutter, F.B., Evaluation of a Trap-Neuter-Return Management Program for Feral Cat Colonies: Population Dynamics, Home Ranges, and Potentially Zoonotic Diseases, in Comparative Biomedical Department2005, North Carolina State University: Raleigh, NC. p. 224.
[3] n.a., Point of View Re: Recent modeling study published in JAVMA advocating that feral cat management utilize vasectomies or hysterectomies rather than traditional spay/neuter or lethal control, 2013, Alliance for Contraception in Cats and Dogs.
[4] Levy, J.K., D.W. Gale, and L.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): p. 42–46.
[5] Nutter, 2005.
[6] Nutter, 2005.
[7] Levy, et al, 2003.
[8] Natoli, E., et al., Management of feral domestic cats in the urban environment of Rome (Italy). Preventive Veterinary Medicine, 2006. 77(3-4): p. 180–185.