The Decline in Feral Cats

A great debate has been raging for several years now about how to control the number of feral cats. On one side of the debate we have wildlife conservationists who argue that the domestic cat is an invasive species that is slaughtering native species and must be eradicated in the same way that other invasive species are eradicated – by killing them all. On the other side we have No Kill advocates who argue that trap-and-kill programs do not work and that feral cat numbers can be managed and gradually reduced by trap-neuter-return (TNR). The two sides have been battling for years, with wildlife biologists successfully opposing TNR in some places.

Underlying this debate is an assumption that has, as far as I can tell from reading the non-paywalled literature, never been addressed in any systematic way. That assumption is that feral cats in the United States are like other “invasive” species such as starlings and Burmese pythons, in that their numbers are rapidly increasing. We see projections that one feral cat can have hundreds of thousands of offspring in a few years, for example. The label “invasive” itself designates a non-native species that comes into an environment and takes over, squeezing out native species by its rapid reproduction. Think kudzu.

What do we know about feral cat population numbers in the United States? The most accurate answer to that question is “nothing.” Over the years various estimates of feral cat populations have been made, often in the range of 60 million. One recent study that attracted a lot of attention estimated that there were from 30 to 80 million un-owned domestic cats in the United States. This estimate was made in a 2013 article by Scott R. Loss, et al., published in the journal Nature Communications. It is often referred to as the Smithsonian study. The Smithsonian study did not report any original research on the number of un-owned cats in the United States; instead, it made estimates ostensibly based on five other studies. The authors of the paper acknowledged, however, that: “No precise estimate of the un-owned cat population exists for the United States . . . .” Because they had no good data on numbers of un-owned cats in the United States, they used data from other countries to estimate what the population might be in the United States. The wide range in this estimate, and the lack of data from the United States, resulted in numbers that I would characterize as “guessing.”

But in spite of the lack of data on the feral cat population nationwide, there are useful things we can say about feral cat distribution and their numbers over time. First of all, as to distribution, domestic cats are a commensal species, and as such their numbers are heavily dependent on the human population. As a commensal species, feral cats live primarily in the cities and suburbs. This is an extremely important fact about feral cats that has been given virtually no attention in connection with control measures. There is no evidence whatsoever that feral cats exist in sufficient numbers to cause damage to populations of native species in wild areas of the territorial United States, away from human habitation. Nor is there any evidence that feral cat numbers in wild areas are increasing. The commensal nature of the cat, and its dependence on its association with human habitation, means that feral cats are not an invasive species in the classic sense of over-running natural habitat and crowding out native species. Since feral cats require resources that they find in human habitations to reach high populations, efforts to control those populations must concentrate in cities and suburbs. We do not need to be concerned about most wild areas, because they have very few feral cats.

In the cities and suburbs where feral cats live, there is not a black-and-white line between feral and tame cats. Although feral and tame cats may be very different behaviorally, they are denizens of the same urban habitat and their populations intertwine. In many colonies you will find feral and tame cats living side-by-side. Therefore, what we are really interested in for purposes of designing control programs is the number of free-roaming cats (aka community cats), whether they are feral or tame.

The two important facts discussed above – that cats are commensal and that the population we are interested in for control purposes is free-roaming cats, point us to an important data source that has been completely overlooked in discussions about the feral cat “problem” – historical animal control data. That data shows us that the population of free-roaming cats in the urban areas where cats actually live has been plunging since the early 1900s. All we need to do to “control” the free-roaming cat population is to figure out what we have been doing right and do more of it.

Free-roaming cats were apparently not considered a problem in American cities until the latter half of the 19th century. In fact, there are references in historical documents to cat shortages. Large numbers of horses and dairy cows were stabled in cities throughout the 1800s, and you could find cats in every stable. Horses ate grain, and cats deterred rodents from getting to the expensive grain. It was not until around the end of the 19th century that the number of cats grew large enough in New York City, Boston, and other large cities that systematic efforts to control their numbers were made. In New York City, that job fell to the ASPCA.

The ASPCA has made their intake and euthanasia numbers available for selected years in the period from 1894, when they were awarded the responsibility for animal control in New York City, to 1994, when they gave up that responsibility. During that 100-year period, the vast majority of animals who were taken into shelters in the city were taken in by the ASPCA. The ASPCA is to be congratulated on their willingness to make this data available, because it is the sole source of shelter intake data that we have that goes back to the early 1900s.

The cat-intake numbers from the ASPCA official reports are astonishing. In 1895 the ASPCA took in 24,140 cats. That number rapidly went up as the ASPCA ramped up its animal control operation. In 1914 the intake number was 177,234, and in 1928 it was 217,774. In 1934 the cat intake number peaked at 219,506 cats. According to unofficial reports, the numbers in some years may have been even higher. One report was that the ASPCA killed 303,949 cats in 1911 (Forbush, The Domestic Cat). But the number of cats impounded by the ASPCA fell sharply from 1934 to 1946, and in 1946 the ASPCA impounded 155,312 cats. The decline continued, and in 1965 the number was 75,858. In 1994, the number was 27,366. The number of cats impounded in New York City continued to decline after the city took over animal control in 1994, and in 2014 cat intake was 18,784. Meanwhile, the human population of New York City increased from 5.6 million in 1920 to 8.5 million today.

If we pick 1920 as a base year and compare it to 2014, we see a dramatic fall in cat intake numbers in New York City, both in absolute numbers and numbers relative to the human population. The number of cats impounded by animal control fell from about 200,000 per year in 1920 to 18,784 in 2014. That is a decline of 91% in absolute numbers. The decline relative to human population was from 36 per 1000 people in 1920 to about 2 per 1000 people today, a 95% drop.

Now, some people (particularly wildlife biologists, I suspect) would criticize these numbers as meaningless. They would argue that the numbers are for only one city and that enforcement as to cats may have changed over the years. These are valid criticisms, but I do not think they invalidate the evidence of a plunge in free-roaming cat numbers.

As to the objection that the numbers are from only one city, we have quite a lot of national data showing a fall in shelter intake across the United States. This fall in intake has been particularly well-documented for the years 1970 to 2000. It is not the quality of data we would ideally like to have for scientific study, but it is consistent across a large number of shelters. Those estimates are that shelter intake nationwide, of cats and dogs, was some 26.5 million in 1970 and about 9 million in 2000. As to the objection that animal-control enforcement may have changed over the years, changes in enforcement up to at least the year 2000 were in the direction of more enforcement against cats, not less. And in any event, we are not looking at a subtle finding here. Plunges in the number of cats impounded on the order that we have seen in the United States is hardly likely to be solely due to changes in enforcement.

Additional evidence that the number of cats in cities has cratered comes from ecological studies that were done in the 1980s. Cat densities of from 725 to 1813 per square mile were found by researcher James Childs in Baltimore neighborhoods in the early 1980s. I am not aware of any more recent ecological surveys of cats in cities, but such numbers of free-roaming cats would surely be very rare in cities today.

So, what happened? Why did the number of free-roaming cats in our cities fall off a cliff? One thing that did not cause the decline in numbers was shelter killing. In spite of massive killing, the numbers of cats impounded in New York City throughout the early 1900s continued to rise. The explanation for the fall in the number of cats was changes in the environment. The great decline in cat intake that we saw in New York City from roughly 1920 to 1945 correlated with the period of time after horses and dairy cows disappeared from the cities. Cats lost their jobs protecting stables, and as the stables disappeared a huge chunk of the food and shelter resources that cats had relied on disappeared with them. Also in the early 1900s, cities began to make organized efforts to improve public health. In addition to getting livestock out of town, cities made big efforts to clean up the streets and get rid of abandoned buildings. Less trash in the streets and fewer abandoned buildings equaled fewer resources for free-roaming cats.

Another enormous change happened in the 1970s as safe, humane techniques for spaying and neutering were perfected and veterinarians began to recommend sterilization for owned pets as a routine part of healthcare. This trend accelerated in the 1990s as pediatric spay-neuter became accepted, and today a very high percentage of owned cats – estimates are over 90% – are sterilized. As more and more owned cats were sterilized, there was less and less seeding of the free-roaming cat population by owned pets. Another factor in the period from 1970 to 2000 was that residences began to secure their trash better. Photographs of Baltimore from the 1970s show alleys full of metal trash cans tipped over by dogs, with the lids scattered around. Today we have garbage cans with locking lids that are much harder for animals to open.

What part did TNR have in all this? TNR did not become widespread until recently, and it may be too early in the process to evaluate long-term effects of TNR on the population of cats in cities and suburbs. However, TNR should further decrease the seeding of the free-roaming cat population. If we could do TNR on a substantial percentage of the population of free-roaming cats in the cities and suburbs, we should see the same type of decline that we saw in feral dog populations from 1970 to 2000.

What more can we do? A 1989 paper by Calhoon and Haspell found that it was the availability of shelter that limited the number of cats in Brooklyn, and that supplemental feeding did not increase cat numbers. If we are serious about reducing the number of feral cats, we need to reduce urban blight, including getting rid of abandoned houses, garages, cars, etc. In the suburbs people must secure their outbuildings. TNR can help transition cats who are affected by these measures so that they can live out their lives in comfort. For example, when people complain about feral cats in their neighborhoods, we could trap, sterilize, and relocate the cats to a safe place, and then counsel the people to secure anything on their property that could potentially serve as shelter for cats.

But really, probably the best thing we can do is just relax. The trend in the number of free-roaming cats has been sharply down, and that trend is continuing. Since cats live mostly in the cities and suburbs, and since populations in those areas have been falling precipitously, we have a system that is actually working very well. We just need to be a little patient, and keep doing what we are doing.

The only thing that might slow us down is the bird conservationists. The bird conservationists see what we are doing as all wrong, and they want us to be forced to throw out everything we’ve worked hard for since 1970 and replace it with catch-and-kill programs. This reminds me of the people who advocate mandatory spay-neuter. Mandatory spay-neuter actually results in fewer animals being sterilized, because such rules drive people underground. Similarly, catch-and-kill programs will result in people hiding feral cats, and being afraid to reveal their presence to anyone. This will mean that fewer feral cats will be sterilized, thus setting back all our gains. Large numbers of feral cats live on private property, and the bird conservationists do not seem to realize that no government can give them the right to go on private property to kill feral cats.

The most effective way to protect our current success from the bird people may be to continue to grow our networks of feral cat caregivers. The reason the bird people have not succeeded so far in setting the clock back is that no mayor or city councilmember in his or her right mind is going to propose a mass extermination of cats. As long as our network is strong, that will continue to be the case. Wildlife conservationists have succeeded in derailing TNR efforts in some places, and that is a shame, but TNR, since it can be done by people on their own property, can exist even where formal programs are banned.

NOTE: Since posts about feral cats tend to get a lot of comments, comments to this post will be limited to one per person. Additional comments can be made on the blog’s Facebook page. As always, comments that do not comply with the comments policy will not be posted.


  1. Wow comes to my mind too. Add in wow this was dumb. You open with saying there is no way to know how many cats there are, then finish with ‘data’ shows the numbers falling since 1900.
    If you know they are falling you must know how many there are, which you said we don’t.

    • We don’t have any good estimate of the number of feral cats nationwide, but we have good evidence that the trend line in population is sharply down. We don’t have to know the actual number to see a trend.

    • The article clearly stated that data on “Feral Cats” was unknown. Later paragraphs address how the ASPCA collected data on “Free Roaming Cats”. . . and that was very rude & childish to call the article ‘dumb’. You needed to just read a bit slower perhaps.
      Feral cats go about their way and find their own food and generally avoid humans. (Although I had one that would come to my house and learned to not fear me.) Free roaming cats are the ones that many persons think they have a ‘pet’ and do put out food for it but do NOT really take care of it as a companion animal. Many people surely didn’t spay or neuter their cats and hence; overpopulation. Thank goodness for all these caring people towards the situation. I have always rescued my companion animals from our local shelters and my daughters are now preparing to continue this as they begin their new lives with their own residences.

  2. Thank you for an informative article. In response to the bird conservationists, I have never felt they looked at the whole issue – that loss of habitat (due to the actions of humans) plays a large (and perhaps the largest) role in the loss of the bird population as well as the population of many other animals. When animals no longer have their native habitat to shelter in, eat in and naturally balance themselves out, they are forced into much closer contact with humans. Bird-eating animals that this has impacted are owls, falcons, hawks, eagles, foxes, coyotes, wolves, weasels, bears (yes bears have climbed trees to eat bird eggs, especially bald eagle eggs), snakes, reptiles and lynx/mountain lions to name a few. For survival, these animals will eat whatever is available. Since the songbirds are forced into a much smaller area as well, they are easier prey for many of these predators. Also, humans who feed birds, create a natural “buffet” for many of these animals. A large number of these animals not only eat birds but are known to kill/eat cats as well which could be one factor in the trend for the decline of free-roaming cats. It’s only my opinion but it seems to me the greatest enemy of birds and all species on this planet is humans and their total disregard for the needs and importance of all species to our ecological balance. Please leave the cats alone – they are fighting as hard to live as any other species on this planet and are far from the only creature out there eating birds.

    • You assume habitat loss and invasive species predation are mutually exclusive. They are not. It’s like saying we should stop all research into curing cancer since heart-disease kills more people. After habitat loss, outdoor and feral cats are the single largest source of bird mortality in the United States. Now ask yourself a simple question, is it easier to curtail human population growth and expansion which is a direct contributor to habitat loss, or is it easier to educate people about the benefits of keeping cats indoors and eliminate feral colonies. Outdoor and feral cats are a human made problem which requires a human made solution. Felis Catus is a domesticated species, by law, any domestic animal needs to be contained. Furthermore, there has not been a single study to show the effects of TNR reducing and eliminating feral cat colonies. A spay rate of 70-90% is required just to halt, not reduce, just halt population growth in a feral colony. TNR groups are very fortunate if they get a 5% spay rate in a colony. Free-roaming domestic house-cats are not part of “nature” or the “circle of life”. They are not “natural” or “God’s creation”. House-cats were developed from African wildcats by man around 10,000 years ago, much in the same way that we started with wolves and now have dachshunds and schnauzers. House-cats were brought to North America a mere 600 years ago. They have no ecological niche in the environment anywhere in North America or the Western Hemisphere. Native birds and animals evolved here together over MILLIONS of years, predator and prey, without the domestic house-cat. Native predators such as hawks, owls, bobcats, mink, etc do kill birds. We accept that because they are native and they belong in the environment here. Those native creatures ARE part of the cycle of life and nature. House-cats, whether they are pets, strays, or ferals do not belong in the environment here. They need to be contained or removed.

      • You say that colony caretakers are lucky if they spay 5% of their animals? That is TOTAL B.S.! I actively TNR between 30-60 animals a month, I have achieved 100% sterilization in 15 colonies, monitor those colonies and have S/N any rare newcomers. I have “closed” 10 colonies over the last 10 years because the animals expired and there were no newcomers or kittens for years. TNR works.

      • Mr Bill where do you get 5%?
        Our nonprofit has TNRed over 9000 cats since 2010. We were are TNRing separately before then too. This year 5 volunteers have TNRed over 2251 cats & prevented over 900 kittens from being born. The colonies are getting less. I see the progress.
        The amount of uninformed people that think that trapping & removing or trap & kill or trap & contain is the problem. You are not going to fix the problem by trap & remove, kill or contain. When cats are removed,the colony senses it’s numbers are depleting, so other cats move in. The new cats are not sp/ntr’d & the colony starts reproducing again.
        I’ve had people that did not want the cats fixed, they wanted them gone. They tried to trap & dump somewhere. Some of the cats found their way back to the colony. Then they brought them to the shelter where the cats were killed. The colony 3 years later had tripled in numbers. The person contacted me again & agreed to TNR. The colony went from 19 plus cats to 5 cats. I also TNRed 60 cats in the surrounding neighborhoods.
        After hurricane Katrina neighborhoods that were always whining that they wanted the cats gone were pleading with us to bring them cats bc rats, mice, rodents & snakes were moving in. Now these neighbors get along well with community outdoor cats.
        TNR works. It does not work when people trap & remove which creates the vacuum effect & cats reproduce faster.
        Your dream of containing outside cats is just that. In the south the weather allows cats to survive winters & have plenty of food to live without a caregiver (or with limited care). They just need to be spay/neutered & vaccinated so they can keep the balance of pests down.
        TNR is the solution. I have closed countless colonies by trapping all the cats & did upkeep for new comers/ or dumped cats.
        Many colonies that I have TNRed back in 1998 -2006 have gone away.
        At least more people are telling us about colonies of cats that need to be TNRed. More people are open to TNR now too.

      • Bill, you are in error on several counts.

        1. Your question: Is it easier to curtail human population growth and expansion which is a direct contributor to habitat loss, or is it easier to educate people about the benefits of keeping cats indoors and eliminate feral colonies? is a malformed question. Most everyone would agree that a reduction in feral colonies is a good thing. The question is how to do it. You argue that trap and kill is the only way; yet that has not worked in the last 50 years it’s been implemented. You also assume people will willingly and on their own time trap all the feral cats and kill them. No one is willing to do that. What people ARE willing to do is TNR.

        2. Cats are not required by law to be indoors. In fact, in some communities, shelters aren’t required to take cats in.

        3. TNR groups being fortunate to get only a 5% spay rate is factually incorrect. I manage five colonies myself and know of many others. All have virtually 100% spay rate, and caregivers continue to trap until they do. In fact, this comment of yours indicates you know NOTHING about feral cats, TNR, or how to best manage the problem, and I stopped reading after that.

      • Our current Eco system is in constant flux. To say that cats are not part of our current Eco system only shows your lack of knowledge in this area, with all do respect. As you say above, cats were brought to North America by man and man is not stupid. Not they were brought here bc they served a purpose, to curb, hopefully eliminate, the massive rodent infestation that was also created by man. Rodents, inadvertently brought here by trade ships, were responsible for spreading disease and contaminating food source for ppl and livestock alike. Are we really going to go with the ” cats are responsible for spreading disease” argument ? Actually cats are responsible for curtailing the spread of disease caused by rodents and insects like roaches. And why is it that the so-called conservationist suddenly go silent when bulldozers come along to knock down the precious ecosystem that thye claim to want to conserve? Do you know how many baby birds and fledglings are wiped out and left half alive, mutilatd and crippled by the bulldozers and downed trees? Let me help you with the math, that would be generations, which would directly effect the trickle down generations that also won’t see the light of day thanks to the “conservationis” not so concerned with conservation at all.

    • I have managed a TNR community cat colony for 3 years now. Prior to that, we had a big problem with cat fights, people’s bird feeders being ransacked and front porches that smelled of urine. Now we have no fights, no urine and since the cats are fed regularly (wet twice daily & dry available always) they do not bother the wildlife. Once, a baby duckling had gotten separated from the group and the cat colony matriarch played with it gently and then lost interest. Next thing I know, the little one is back with his family. Same thing happened when a pre-fledged bluejay fell from the nest. They were interested but they showed no interest in eating him. (I put him on a branch and he ‘flutter-hopped’ his way up back to the nest.) Feral cats have to eat, and bugs, rodents, birds and reptiles are their lunch, but feral/stray TNR colony cats are not a problem for the wildlife. Our feral cat population is stable and trouble-free. They watch my bird feeder with interest and chase squirrels ~ but its a game for both parties involved. TNR is the solution ~ TNR works.

    • Thanks Anne. For those who may be interested, I have a copy of the book and can give you my impression of the study. It was an internet survey of 1500 people, selected to be a representative sample. The results of the study as to owned cats are similar to results of other surveys about owned cats I’ve seen such as APPA, but Beall’s survey had more detail on feral cats and I think it might be of interest to people who care about this issue. The gold standard, of course, would be boots-on-the-ground surveys where cats in a given area are actually counted, but I’m not aware of that having been done over a significant area since the 1980s.

  3. I’m not relaxing. TNR and colony care is tough work, and made tougher by landlords and HOAs that want cats o-u-t. We are being persecuted as caregivers. I was threatened with eviction and now I have evidence they are killing the cats I saved through TNR. I have no one at my back, not even the Fairfax County Shelter who sponsors the TNR program will back me up. They are dong a quantity, not quality program.

  4. I live in a neighborhood where 3-4 of us have actively and successfully implemented TNR when a growing feral cat population was becoming a serious problem. Something had to be done, so we invested our time and effort to TNR every cat in the colony. The population not only stopped growing, but has dropped through natural attrition. In 4 years, we’ve had no new kittens, no new incomers and the numbers have dropped by nearly 45%. The caregivers provide food, water and outdoor shelters, which clearly reduces the cats’ interest in other outdoor wildlife. There are some neighbors who just don’t like cats, and they will find or manufacture any number of arguments to deny the success of TNR, yet while these fools complain about what we did, they themselves did absolutely nothing. They are basically the kind of people that everyone loves to hate, and they just keep providing reasons for not liking them. But when you listen to their arguments, they are clearly rooted in ignorance, have no regard to remaining factual and are riddled with nothing bu their personal opinions. To my way of thinking, none of us asked for this problem, but at least some of us did something to control it. We opted for TNR, and we have the tangible, visible and verifiable proof to support our claim that it absolutely does work. If these idiots knew what this neighborhood would be like if we’d done the same thing they did–NOTHING, maybe they’d shut up. People are ignorant and self-absorbed in their own personal agendas. Some people just cant see past themselves to see viable solutions that do work, even if not exactly the way they want them to.

  5. I think that Bill’s comment was not clear. The spay rate within a colony may well be 100%, but less than 4% of feral cats are within such colonies. Thus we have a small number of cats in the total population being neutered and the overall population increasing. Is there anyone out there suggesting that we will sometime have the 70-80% of the total feral cat population (the percent required to keep cat populations steady) neutered at some point?
    As to the claim that feral cats are in decline: this flies in the face of the proposals being made by TNR proponents to municipal boards across the country: “We can save you from your burgeoning cat population.” And we have headlines like the one from Niagara Falls, NY, saying that the city has more feral cats than humans. You cannot have it both ways.
    Of course, wildlife biologists oppose TNR. These programs support cats that are decimating our bird and small animal populations. FWS breeding bird statistics show a decline in songbirds of about 2/3, and there is plenty of evidence to indicate that cats are playing a major role in this decline.
    Finally, feral cats are not commensal any more than those raccoons that steal food from colony feeders. They have fared very well on their own on islands where early explorers left them. There they have contributed to the violence done to seabird colonies.

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