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Replacing Myth with Math: Using Evidence-based Programse to Eradicate Shelter Overpopulation.INTRODUCTION

The toll has been staggering: during the last 40 years, more than 250 million cats and dogs have been put to death at animal shelters in the United States. As one veterinary epidemiologist put it " (o)f all the issues affecting the welfare of companion animals in the United States, there can be none larger in scope, greater in magnitude, longer in duration, or more worthy of disgrace than that of pet overpopulation. " i

At the peak in the 1970s, more than a fifth of all the cats and dogs in the country met their death in shelters every year. Little formal research had been done to understand the causes of overpopulation or assess the effectiveness of possible interventions. Sheltering costs consumed the budgets of animal control agencies and humane societies; they spent very little on pet sterilization or other preventive programs.

Much has changed over the past 15 years. We have learned a great deal about the dynamics of cat and dog populations. We know much more than we did about how cats and dogs become homeless and why. And governments and foundations now spend tens of millions of dollars every year on programs to reduce overpopulation.

Greater resources and understanding should have accelerated our progress in reducing overpopulation, but it has not. In recent years we have made less progress, not more. During the past ten years, the number of cats and dogs put to death in shelters has dropped by only one per cent a year compared to an average decline of three per cent a year for the previous thirty years (See Figure 23 in Chapter 6).

What accounts for the slower gains? One likely reason is that as fewer animals enter shelters, programs must be targeted more accurately to those that remain at greater risk of impoundment to make further progress. Recent research has identified some of the characteristics of animals and their owners that increase this risk, but shelter overpopulation programs have not used that information to its full advantage. For the most part, researchers and people who put together shelter overpopulation programs have lived in separate worlds, isolated from each other. As a result, program designers have rarely made use of research findings to effectively target their programs.

This book attempts to fix that by creating a crosswalk between the worlds of shelter overpopulation researchers and people who develop remedial programs. It includes:

  • Concrete and comprehensive recommendations about how animal control agencies, veterinarians, humane societies, and advocacy groups can employ shelter statistics and data from surveys and research studies to reduce shelter overpopulation in their communities;

  • Suggestions about future research that could increase shelter adoption and pet retention rates and improve the effectiveness of pet sterilization and feral cat management programs;

  • Summaries of significant research findings and suggestions about how they can be used to full advantage in program design and implementation.

Despite the slower progress of recent years, there is reason for hope. The slower pace has not been universal; some communities have sustained the momentum of earlier years. Some have even eliminated the use of population control euthanasia in their shelters. Without exception, people in these communities have made great use of data to inform and drive their shelter overpopulation programs. This is an important lesson.

Many thanks to Ed Boks, Caroline Boyd, Rick DuCharme, Jennifer Fearing, Dr. Joshua Frank, Dr. Frank Hamilton, Dr. Kate Hurley, Bob Marotto, Esther Mechler, Dr. John New, Jr., Dr. Sandra Newbury, Dr. Gary Patronek, Dr. Sara Pizano, Aimee St. Arnaud, Dr. Margaret Slater, Dr. Richard Speck, Bert Troughton, Heidi Weimer, Dr. Alexis Wenstrup, John Wenstrup and Dr. Stephen Zawistowski for their generosity in reviewing parts of this book. Special thanks to Rick Hall for his suggestions about how to improve the manuscript, to Donna Maurer for the patience and precision of her editing work and to Bunny Stoykovich for the grace and warmth with which she has put this book together. And, most of all, thanks to Roxanne and our children, Moriah and Ethan, for sharing me with this project, generously and without complaint.

Concord, New Hampshire
January, 2010

 i Kass PH (2007). Cat Overpopulation in the United States. The Welfare of Cats, I. Rochlitz (ed.) New York, N.Y.: Springer Publishing, 119.


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Chapter 1
(26 pages)
Replacing Myth With Math: Using Data to Design Shelter Overpopulation Programs
Chapter 2
(16 pages)
Animal Care and Control Agencies
Chapter 3
(14 pages)
Veterinary Practitioners
Chapter 4
(21 pages)
Humane Societies and Rescue Groups
Chapter 5
(20 pages)
Advocacy Groups
Chapter 6
(13 pages)
Building Evidence-Based Programs to Eradicate Shelter Overpopulations
  Glossary of Terms
Appendix A.
(24 pages)
Research Articles
Appendix B.
(1 page)


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