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    Cats

    Cats: Fewer kittens born to the street.

    Millions of cats live outdoors or pass through shelters every year. Sterilizing enough of them, steadily, brings their numbers down; doing a little everywhere barely helps.

    Try it in the sliderTalk to Ryan

    Ryan K. Hertel · heyitskenton

    The problem

    What we're up against.

    • Tens of millions outdoors.

      An advocacy group estimates 30 million to 40 million community cats in the United States, and estimates vary widely.

    • Shelters carry the load.

      In 2025, 3 million cats entered US shelters and rescues, and 277,000 were euthanized.

    • Kitten season keeps coming.

      Between January and June 2026, 674,000 kittens entered shelters and rescues, and the number of cats coming in was still rising.

    What works

    Proven, and ready to grow.

    • High intensity, citywide.

      In a twelve-year field experiment in an Israeli city, cat numbers began to fall only once more than 70% of cats across the city were neutered, and then by about 7% a year.

    • Aim where the kittens come from.

      Concentrating sterilization on one high-intake area cut the shelter's cat intake from it by 66% in two years, against 12% elsewhere in the county.

    • Shelters that sterilize and return.

      Across six US shelters, community cat programs brought a median 32% fall in cats taken in, and an 83% fall in cats euthanized.

    • It can pay for itself.

      An Australian council's free sterilization program cut cat intake by 66% and euthanasia by 82% over eight years, and saved it AU$440,660 for AU$77,490 spent on surgery.

    What a family could fund

    Where the money goes furthest.

    • A low cost per cat.

      Surgery, a vaccine and return average about $59 a cat, before trapping and overhead, and plans led by sterilization cost less than removal-only plans.

    • Clinics built for volume.

      The ASPCA says its program helped open more than 200 high-volume spay and neuter clinics, which sterilized more than 13.6 million animals from 2005 to 2024.

    • A backlog to clear.

      Since the pandemic, the shortfall in spay and neuter surgeries is estimated to have grown to 3.7 million.

    Honest limits

    What money can't promise.

    • Patchy programs fail.

      Analyzes of two large county programs found no consistent drop in cat population growth. Models find little effect unless more than 57% of cats are sterilized or removed each year.

    • Colonies refill.

      In Rome, about 21% of colony cats were newcomers, abandoned or wandering in. In Israel, highly neutered areas didn't shrink, presumably because cats moved in.

    • Cats hunt wildlife.

      Cats kill an estimated 1.3 billion to 4 billion birds a year in the contiguous United States, mostly unowned cats.

    • Capacity is short.

      Spay and neuter capacity has shrunk since the pandemic, though experts haven't agreed on whether there's a general shortage of vets.

    Hard questions

    Asked and answered.

    1. You might ask

      Why cats, when people need help?

      Ryan

      That's each family's choice to make, and the slider leaves it to them. It costs little per cat, every visit includes a rabies vaccine, and cats are the domestic animal most often found with rabies in America.

    2. You might ask

      Don't outdoor cats kill birds?

      Ryan

      Yes, in very large numbers, and mostly unowned cats. Some scholars argue the harm isn't a disaster everywhere. Either way, sterilizing cats only helps wildlife if it truly brings their numbers down, which is why this plan funds intense, steady work in one place at a time.

    3. You might ask

      Does trap-neuter-return really shrink colonies?

      Ryan

      Only with high, steady, citywide coverage: the Israeli study found it works only when done with high intensity, continuously, and across connected areas. Patchy programs often fail.

    In the slider

    See what your fortune could do here.

    Cats

    The slider prices this cause with these numbers:

    • About $59 a cat to spay or neuter, vaccinate and return to its colony.
    • The whole need here is the low end of estimates of America's community cats, 30 million.
    • Some of those cats are already fixed, and colonies refill without steady work, so this is an upper bound.
    Try it in the sliderTalk to Ryan

    More of the Blueprint

    Keep reading.

    23 more chapters on the way

    Back to Keep 100

    Sources

    Every number in this chapter, and where it came from.

    1. Source 1: Reduction of free-roaming cat population requires high-intensity neutering in spatial contiguity to mitigate compensatory effects (Gunther and others) (opens in a new tab)

      PNAS, 4 April 2022. Checked 16 October 2026.

      A controlled field experiment over twelve years in an Israeli city.

    2. Source 2: Estimation of effectiveness of three methods of feral cat population control by use of a simulation model (McCarthy, Levine and Reed) (opens in a new tab)

      Journal of the American Veterinary Medical Association, 1 August 2013. Checked 16 October 2026.

      A simulation model.

    3. Source 3: Outdoor cats FAQ (opens in a new tab)

      Humane World for Animals. Checked 15 October 2026.

      Estimates vary widely. This is the low end of the publisher's range.

    4. Source 4: 2025 Annual Data Report (opens in a new tab)

      Shelter Animals Count. Checked 16 October 2026.

      A national database of shelters and rescues, run as an ASPCA program; national figures are modeled from the organizations that report.

    5. Source 5: Shelter Animals Count Releases 2026 Mid-Year Data Summary and New Interactive Data Explorer Featuring 10 Years of Analysis (opens in a new tab)

      ASPCA, 6 October 2026. Checked 16 October 2026.

    6. Source 6: Effect of high-impact targeted trap-neuter-return and adoption of community cats on cat intake to a shelter (Levy, Isaza and Scott) (opens in a new tab)

      The Veterinary Journal, 2014. Checked 16 October 2026.

      A two-year program in one Florida zip code, compared with the rest of the county.

    7. Source 7: Integrated Return-To-Field and Targeted Trap-Neuter-Vaccinate-Return Programs Result in Reductions of Feline Intake and Euthanasia at Six Municipal Animal Shelters (Spehar and Wolf) (opens in a new tab)

      Frontiers in Veterinary Science, 21 March 2019. Checked 16 October 2026.

      Before-and-after results at six US shelters; a co-author works for Best Friends Animal Society.

    8. Source 8: Impact of a Local Government Funded Free Cat Sterilization Program for Owned and Semi-Owned Cats (Cotterell and others) (opens in a new tab)

      Animals, 29 May 2024. Checked 16 October 2026.

      Eight years in Banyule, a city council in Victoria, Australia.

    9. Source 9: Guidance for management of free-roaming community cats: a bioeconomic analysis (Benka and others) (opens in a new tab)

      Journal of Feline Medicine and Surgery, 29 November 2021. Checked 15 October 2026.

      Surgery, an ear tip, a rabies vaccine, short-term care and return, averaged across the agencies studied, before overhead and trapping.

    10. Source 10: Championing Spay/Neuter Helped Define ASPCA in the 20th Century and Beyond (opens in a new tab)

      ASPCA, 18 February 2026. Checked 16 October 2026.

      The ASPCA's own figures.

    11. Source 11: The pandemic's cruel aftermath: progressive decline in spay/neuter capacity (Guerios, Clemmer and Levy) (opens in a new tab)

      Frontiers in Veterinary Science, 21 March 2025. Checked 16 October 2026.

      Data from high-volume clinics, 2019 to 2023.

    12. Source 12: Analysis of the impact of trap-neuter-return programs on populations of feral cats (Foley and others) (opens in a new tab)

      Journal of the American Veterinary Medical Association, 1 December 2005. Checked 16 October 2026.

      Programs in two large counties, in California and Florida.

    13. Source 13: Management of feral domestic cats in the urban environment of Rome (Natoli and others) (opens in a new tab)

      Preventive Veterinary Medicine, 10 October 2006. Checked 16 October 2026.

    14. Source 14: The impact of free-ranging domestic cats on wildlife of the United States (Loss, Will and Marra) (opens in a new tab)

      Nature Communications, 29 January 2013. Checked 16 October 2026.

      The corrected estimate, published in December 2013.

    15. Source 15: The United States veterinary workforce dilemma: are we asking the right questions? (Neill and Salois) (opens in a new tab)

      Journal of the American Veterinary Medical Association, 11 September 2024. Checked 16 October 2026.

    16. Source 16: Rabies surveillance in the United States during 2024 (Keshavamurthy and others) (opens in a new tab)

      Journal of the American Veterinary Medical Association, 31 August 2026. Checked 16 October 2026.

    17. Source 17: A moral panic over cats (Lynn and others) (opens in a new tab)

      Conservation Biology, 3 June 2019. Checked 16 October 2026.

      An essay arguing the other side of the debate.