Posted on 04/25/2009


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Position Statement on Mandatory Spay/Neuter Laws

Nationwide, per capita shelter intake and euthanasia have been in a steady decline for the past several decades and research indicates that the main reason for this decline is the increasing incidence of spayed and neutered animals in the pet population (Zawistowski et al., 1998; Irwin, 2001; Clancy & Rowan, 2003). In fact, the veterinary community recently formally acknowledged the importance of safe, efficient, accessible sterilization programs as the “best antidote to the mass euthanasia of cats and dogs resulting from overpopulation” (Looney et al., 2008). There is, however, variation in the trend in shelter intake and euthanasia decline across communities as well as a difference between that for dogs and cats. As a result, many communities are currently searching for methods to reach the segments of the animal-owning population that are still contributing disproportionately to companion animal overpopulation. Attempts to reduce shelter intake and euthanasia through the passage of legislation mandating the spaying and neutering of companion animals has recently garnered much attention and debate.

To the knowledge of the ASPCA, the only method of population control that has demonstrated long-term efficacy in significantly reducing the number of animals entering animal shelters is the voluntary sterilization of owned pets (Clancy & Rowan 2003; FIREPAW, 2004; Secovich, 2003). There is also evidence that sterilizing very specific, at-risk sub-populations of companion animals such as feral cats and animals in shelters can also contribute to reductions in overpopulation (Zawistowski et al., 1998; Clancy & Rowan 2003; Levy et al., 2003; Lord et al., 2006; Natoli et al., 2006). In contrast, the ASPCA is not aware of any credible evidence demonstrating a statistically significant enhancement in the reduction of shelter intake or euthanasia as a result of the implementation of a mandatory spay/neuter law.

Caution must therefore be applied when interpreting existing claims regarding the effects of local mandatory spay/neuter (MSN) laws. First, because nationwide per capita shelter intake and euthanasia generally are in decline due to voluntary spaying and neutering, it is impossible to determine the effect of an MSN law without comparing a community’s trends in shelter intake and euthanasia for several years before and after the law was enacted to trends in adjacent, similar communities without MSN legislation. Furthermore, to discern with confidence the effects of any spay/neuter program on the animal population, which naturally fluctuates somewhat from year to year, population trends must be examined over a period sufficiently long to absorb those natural fluctuations; claims based on one or two years of data can be misleading.

In addition, it is imprudent to generalize about the effects of MSN laws. One reason is that the definition of “mandatory” varies greatly across communities. In some localities, a citation may be issued for any animal over the age of 4 months seen unaltered, while in other communities a citation results only when another animal control offence has been committed or if more than one unspayed female animal lives in the household. Another complication is that it can be extremely difficult for even a veterinary professional to visually determine if an animal, particularly a female, has been sterilized; it would be virtually impossible for an animal control officer to make those determinations in the field. For these reasons, and due to variation across communities in law enforcement funding and personnel support, actual enforcement of MSN laws varies widely, making comparisons between MSN laws or predictions about their impact very difficult.

Another reason for caution when interpreting the effects of MSN legislation is that shelter intake and euthanasia statistics are often presented as a total of dogs and cats. In some communities, the number of dogs entering and being euthanized in shelters is dropping significantly while the number of cats is declining more slowly or even increasing. Therefore it is critical to examine population and shelter statistics for dogs and cats separately, so that reductions in dog intake and euthanasia do not mask increases in cat intake and euthanasia. This issue is particularly critical in the analysis of the effect of MSN laws, since feral and unowned stray cats continue to represent a substantial proportion of the shelter population and euthanasia. This major contributing factor is not addressed by MSN laws that, by nature, target owned animals.

Even when an MSN law seems to have a positive effect on one aspect of animal welfare, it may have a negative effect on another. For instance, in at least one community that enacted an MSN law, fewer pets were subsequently licensed, likely due to owners’ reluctance to pay either the high fee for keeping an unaltered animal or the fee to have the pet altered (Office of Legislative Oversight, 1997).

The ASPCA is also concerned that some communities may rely primarily or exclusively on MSN legislation to reduce shelter intake and euthanasia even though the animal shelter population is actually very heterogeneous, with no single cause or source (National Council on Pet Population Study and Policy, 2001). Many social, cultural and economic factors as well as animal health and behavioral issues contribute to shelter intake; therefore no single program or law can be relied on to solve the problem.

Furthermore, one of the main barriers to spaying and neutering of pets is accessibility of services, which is not addressed simply by making spaying and neutering mandatory. Cost is one of the primary barriers to spay/neuter surgery in many communities (Patronek et al., 1997; Ralston Purina, 2000; Frank, 2001). In fact, low household income and poverty are statistically associated with having a sexually intact cat (Patronek et al, 1997), with relinquishment of pets to shelters (Patronek et al., 1996), and with shelter intake (Frank, 2003). As a result, the proportion of pets from poor communities who are being euthanized in shelters remains high; shelter euthanasia rates in the poorest counties in states including California and New Jersey are several times higher than those in the most affluent counties (Handy, 2002; Marsh, 2008). Each community is unique, however, in terms of the particular sources and causes of companion animal overpopulation and the primary barriers that exist to having pets altered. No one-size-fits-all solution is therefore possible. In examining communities around the country that are having significant success in reducing companion animal overpopulation, it appears that the common denominator is a multifaceted, targeted community program that:

  • Is based on careful research to determine which segments of the animal population are actually significantly contributing to shelter intake and euthanasia and then targets efforts to those segments of the population;
  • Focuses on the particular barriers to spay/neuter that are predominant and strives to overcome them;
  • Is well-supported and well-funded; and
  • Has an efficient voluntary spay/neuter infrastructure in place to service the populations it targets.

ASPCA Position
Based on currently available scientific information, the ASPCA strongly supports spay/neuter as an effective means to reduce companion animal overpopulation. In particular, the ASPCA supports voluntary, affordable spay/neuter programs for owned pets, Trap-Neuter-Return (TNR) programs for feral cats and the mandatory sterilization of shelter animals and of certain individual, owned animals based on their or their owners’ behavior (such as animals deemed dangerous under local ordinances or those repeatedly caught at-large). In order to assure the efficacy of any spay/neuter program designed to reduce shelter intake and euthanasia, the ASPCA believes that each community must conduct credible research into the particular causes of relinquishment and abandonment and the sources of animals in its shelters, including the barriers to spay/neuter services that are faced by those populations contributing disproportionately to the problem. Each community must address these issues with a tailored, multifaceted approach as described below:

  • The community should have in place an adequately funded, readily accessible, safe, efficient, affordable spay/neuter program.
  • Community research should identify the particular segments of the population that are contributing disproportionately to shelter intake and euthanasia, and the community should produce programs that are targeted to those populations.
  • The community should strive to maximize the accessibility of spay/neuter services and provide compelling incentives to have the surgery performed.
  • The spay/neuter program should be developed with the guidance of veterinary professionals who are committed to delivering high quality spay/neuter services to all patients (Looney et al., 2008).
  • The program must adequately address the contribution that feral and stray animals make to overpopulation.
  • The program must be adequately supported in terms of financing, staffing and infrastructure.
  • The efficacy of all aspects of the program must be monitored and revisions made as necessary to achieve its goals.

In summary, the ASPCA recognizes that sterilization is currently the best method to reduce companion animal overpopulation, and therefore to reduce shelter intake and euthanasia. The most important step a humane community can take to decrease companion animal overpopulation is to make a safe, effective, voluntary spay/neuter program available and readily accessible to the community, with programs and incentives targeted to the populations known to be contributing disproportionately to shelter intake and euthanasia.


Clancy, E. A., Rowan, A. N., 2003. Companion animal demographics in the United States: A historical perspective. In: Salem, D. J. & Rowan, A. N. (Eds.), State of the Animals II: 2003. Humane Society Press, Washington, DC, pp. 9-26.

The Foundation for Interdisciplinary Research and Education Promoting Animal Welfare (FIREPAW). 2004. Cross-program statistical analysis of Maddie’s Fund programs, Williamstown, MA.

Frank, J., 2001. Executive summary of research results for: the economics, ethics, and ecology of companion animal overpopulation and a mathematical model for evaluation of the effectiveness of policy alternatives. Houston, TX: The Foundation for Interdisciplinary Research and Education Promoting Animal Welfare.

Handy, G., 2002. Animal Control Management: A Guide for Local Governments. International City/County Management Association, Washington, D.C.

Irwin, P. G., 2001. Overview: The state of animals in 2001. In: Salem, D. J. & Rowan, A. N. (Ed.), The State of the Animals 2001. Humane Society Press, Washington, DC, pp. 1-19.

Levy, J. K., Gale, D. W., 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 Association 222, 42-46.

Lord, L.K., Wittum, T.E., Ferketich, A.K., Funk, J.A., Rajala-Schultz, P., Kauffman, R.M., 2006. Demographic trends for animal care and control agencies in Ohio from 1996 to 2004. Journal of the American Veterinary Medical Association, 229, 48-54.

Marsh, P., 2008. Analysis using data from New Jersey Department of Health and Senior Services (1998) and the California Department of Health Services (1995).

National Council on Pet Population Study and Policy, 2001. Exploring the surplus cat and dog problem: Highlights of five research publications regarding relinquishment of pets. New London, MN. Online at

Natoli, E., Maraglioano, L., Cariola, G., Faini, A., Bonanni, R., Cafazzo, S., Fantini, C., 2006. Management of feral domestic cats in the urban environment of Rome (Italy). Preventative Veterinary Medicine 77, 180-185.

Office of Legislative Oversight, OLO Report 97-3: An evaluation of Bill 54-91, Revisions to the county’s animal control law. June 24, 1997. Montgomery County, MD.

Patronek, G. J., Lawrence, T. G., Glickman, T., Beck, A. M., McCabe, G. P., Ecker, C., 1996. Risk factors for relinquishment of cats to an animal shelter. Journal of the American Veterinary Medical Association 209, 582-588.

Patronek, G. J., Lawrence, T. G., Glickman, T., Beck, A. M., McCabe, G. P., Ecker, C., 1996. Risk factors for relinquishment of dogs to an animal shelter. Journal of the American Veterinary Medical Association 209, 572-581.

Patronek, G. J., Beck, A. M., Glickman, T., 1997. Dynamics of dog and cat populations in a community. Journal of the American Veterinary Medical Association 210, 637-642.

Ralston Purina, 2000. The state of the American pet: A study among pet owners.

Secovich, S. J., 2003. Case study: companion animal over-population programs in New Jersey, New Hampshire, and Maine and a new program for Maine. Master’s thesis, Public Policy and Management. University of Southern Maine.

Zawistowski, S., Morris, J., Salman, M. D., Ruch-Gallie, R., 1998. Population dynamics, overpopulation, and the welfare of companion animals: new insights on old and new data. Journal of Applied Animal Welfare Science 1, 193-206.