How Many Feral Cats Are There? — Spay/Neuter and TNR

No One Knows.  There are people out there who say they do, but they don’t really.

I went to a volunteer orientation at my local shelter, and read through their web page first.  So when the instructor said there were 20,000 feral cats in our county, I pointed out that their website said 40,000.  (Or maybe it was the other way around.)  I fear I have previously annoyed them with undiplomatic questions and I should have known better than to ask that one.

I posted before about some formulae for estimating an area’s population.  I could probably give you a more accurate guess if I drove around.  The I saw a post on FB quoting a number even higher than the max number I’d gotten, so I did a little research on just estimates, not formulae and thought I’d share some of the results.

“There are an estimated 70 million feral and stray cats in the United States” but they don’t say who estimated that or how.

“No one knows how many feral cats there are in the U.S., and estimates are wide ranging (credible estimates range from 13 million to 87 million).” I’m willing to believe it’s somewhere in that range. LOL. Image

Again, no clue where these estimates are from, what they’re based on and why they’re credible.

“Based on this data, a formula was developed to estimate free-roaming cat populations in communities: 0.5 cats/household using US census figures.” from That’s how I got the 57 million figure — They cite another study as the source of their 70 million estimat Dabritz HA, Conrad, PA. Cats and Toxoplasma: Implications for public health. Zoonoses Public Health. 2010;57:34-52, and I haven’t found a free version of that online yet.


This blog has been in my “Drafts” folder for months and I don’t remember what I was planning to add to it, so I’ll just post it.

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New Years Resolution: blog more

HRC’s just updated this with CA’s 2013 data.


They continue to show good effects for s/n clinics.

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Oregon update: More good news thanks to spay/neuter

I’m too excited to wait for the final polish on some of these charts.image005 image028 image054 image062


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The Infertile Crescent: North Carolina’s Spay/Neuter clinics’ impact

If you study the NC map I posted last blog, you will notice areas of low shelter euthanasia near spay/neuter clinics that I’ve dubbed “The Infertile Crescent.”

NC has a statewide license-plate s/n voucher program, and is the home of the Humane Alliance, probably the result of their pet overpopulation — one of the highest state rates of shelter intake and euthanasia I’ve seen.  But things are improving by leaps and bounds in some areas serviced by high-volume spay/neuter clinics.  I looked at the Gaston area in a previous blog.

The Fix A Friend clinic opened in Brunswick County just 8 months ago.  Previously, they had been benefiting from the Cape Fear Clinic in New Hanover County, but with the increase in volume, the Brunswick shelter has seen an improvement in the first 1 months of 2014 compared to 2013.


I’m really looking forward to watching this area.


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The 2013 North Carolina shelter statistics report is out!

The 2013 NC data is out! or download my spreadsheet


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Oregon is a model for the effectiveness of Spay/Neuter clinics

All Oregon w adoptions sn may 1 14

Yes, this chart really is a summary of an awful lot of information.  Not theory.  Not a projection from a small sample.  It includes information from every shelter in Oregon that I know about (well, there’s one for-profit shelter in NE Oregon I don’t have info on) and many rescues.  I have access to fairly ON logodetailed records from the s/n clinics, as I was involved in the Oregon Neutermobile (I named it and made the logo) from the start and most of the clinics were started by ON’s local hosts.

I don’t have data from each shelter for each year, but values for the missing years were interpolated to keep the totaled values reasonably accurate.  There were also a few cases where there were obvious typos, and those values were replaced by interpolations, too.

Notice that, with all the effort put into promoting adoptions all these years, although adoptions have increased, it’s been only very slowly and not nearly enough to reduce euthanasia significantly.

I am sickened by what is happening in Alabama. 10 coverc

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Spay/Neuter clinics benefit a wide area: example, Foothills clinic in Catawba County, NC

While limiting intake, increasing adoptions, or Shelter-Neuter-Return can improve a shelter’s Live Release Rate, they can result in putting the burden of killing on neighboring shelters. Opening a s/n clinic, however, benefits the neighbors as well, as happened when the Foothills s/n clinic opened in North Carolina in 2007.


Intake and euthanasiimage004 - Copyimage003a dropped, or at lease held steady, all around.






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Map of Dog Return to Owner Rates by County in NC, VA, DE and NJ

Map of Dog Return to Owner Rates by County in NC, VA, DE and NJ

I made this while puzzling, again, over NC’s low dog RTO. Looking at census stats, RTO correlates highly with the average income. And not so bad with percentage of residents who majored in Engineering.

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Great progress toward a No Kill Nation (NOT)

Rich Avanzino was interviewed on the radio this morning and says we need only do another 2.3 million adoptions from shelters to become a No Kill Nation. That’s quite a lot of progress, down from 2.7 he said where needed in an interview with him just pubbed on the web yesterday.  And that’s down from the 3 million I’ve seen before.


At this rate, we’ll be at No Kill status by the end of the week.

As I discussed in a previous blog, we don’t really know how many pets are in this country, much less how many people will be adopting next year.  I think the day after I published my blog, this article came out. Americans own 70 million dogs and 74 million cats, and pet ownership is waning. Or no, wait. It’s 83 million dogs and 96 million cats, and pet ownership is at a record high.”

Where does the 17 million new homes come from?  I thought it was from the number of pets, figuring the average lifespan at 10 years and that most people will get a new pet after they lose one, more or less, what with the human population growing, people dying, it probably about balances out.  And if we average those ownership numbers, that comes out to 16.15 million folks getting new pets next year.  Which is sort of close to 17 million.  But how many will already be getting them from shelters?

Well, I based one estimate on Maddie’s Fund’s db of shelter stats for 2011, which represents about 10% of the nation’s human population and I got 1.9 million: 963,454 cats and  931,431 dogs.  But then I looked at California’s shelter stats, also about 10% of the US and also about 1.9 million adoptions.  Except based on CA, it would be 669,601 cats and 1,220,308 dogs.  Well, everyone else seems to think dogs and cats are interchangeable, so why should I worry.  The total number came out almost the same and that impressed me.

Then I looked at these stats:

where obtained



And, by gum, the percentages adopted are close enough that based on either source, it comes to almost 13 million new homes for pets.  Well, that’s not that far from 16.1 which isn’t far from 17.  So we’re sort of on track.

And I will continue along this track in a future blog.


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Modeling cat population growth and decline: tipping point of spay/neuter

I made a lovely little model in Excel, letting me play with all kinds of variables.  The most amazing thing is, no matter what I put in for those variables, there’s a tipping point, where just a few more spay/neuter surgeries per year will bring the population under control, and you only have to go back to maintenance level of s/n, while with less, it’s runaway growth.image001image002

Of course, the real world isn’t so precise.  And there are a lot of factors that will put the brakes on the population explosion.  I put a couple in: that population above a certain level increases infertility and kitten mortality and even higher, 1/4th of the population will die of starvation or disease.  But even that wasn’t enough to slow things down much.

This model doesn’t make a distinction between owned and unowned cats.  In the real world, owned cats are abandoned and unowned kittens are tamed and adopted.  Besides, what difference does it really make in the population dynamics?  A higher proportion of ferals would mean a lower life span and higher kitten mortality, and probably a lower initial % fixed at the start.  All those are variables in this model.

It’s interesting that if shelter deaths are factored in, the tipping point goes down by only about half of shelter death rate.

The biggest factors affecting how many surgeries need to be done to reach the tipping point are the spay/neuter TNRkitten mortality rate and number of litters per year.  These values are probably very local, especially for the feral population, depending on weather and the activity of animal rescuers.

Note, this model assumes that there’s 10% of the unfixed population that will never be fixed.  They could be ferals that can’t be trapped or cats whose people just refuse.  And if a miracle happens (or a programming error, but that’s less likely) and they all get fixed, 10 pregnant cats will materialize out of thin air.  (If you’ve ever tried to TNR a whole colony,  you know it happens.)

I’ll be blogging more about this model in the future and I’ll even give you an equation to calculate the tipping point.

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