The Commensal Cat

Cats are commensal animals. This fact has some very important implications for trap-neuter-return (TNR) and for the battle to save cats from bird conservationists.

black catThe term “commensal” refers to a creature that benefits from its association with another animal without directly hurting or helping that animal. Some of the most common species that live in a commensal relationship with humans are bacteria, rats, mice, and medium-sized carnivores (mesocarnivores). Examples of mesocarnivores are raccoons, foxes, coyotes, and the domestic cat. Domestic cats have a commensal relationship with humans that ranges from pet to feral. Another term that is sometimes used to describe the relationship between domestic cats and people is “mutualism,” which refers to a relationship between two species where both benefit.

The mesocarnivores who live in a commensal or mutual relationship with humans generally combine scavenging with predation in order to survive. Their populations differ from populations of wild animals in several respects, including higher numbers, smaller territories, opportunistic feeding, and a tolerance of human presence. The literature about the domestic cat in the United States contains very little information on the implications of commensalism. Most studies on control of feral cat populations and cat predation seem to assume the commensal nature of the cat without really addressing its implications. This is a mistake, because management of commensal species is, or should be, completely different from management of populations of wild animals who seek to avoid contact with humans. The commensalism of the domestic cat presents us with both problems and opportunities in controlling their numbers.

There is so little that has been written specifically about commensalism in domestic cats that I had difficulty finding anything that was available to the general public on the issue. I finally found an excellent book by an English professor of archeology, Terry O’Connor, that deals with the subject of commensalism in general and has a section on cats. The book is called “Animals as Neighbors: The Past and Present of Commensal Species.” Although the book does not connect the dots between the commensalism of the cat and control techniques such as TNR and Return-to-Field (RTF), it does provide a broad general background on commensalism itself – how it developed over human history and where the various types of commensal animals fit into the scheme.

As O’Connor notes, feral cats “rely on our built environment and garbage for protection and food.” In other words, feral cats thrive in environments where there are a lot of vacant, unused structures and accessible trash. This has been confirmed by ecological studies that were done in Baltimore and Brooklyn in the 1980s. So what does this mean for our feral cat programs?

First and most obviously, feral cat overpopulation is primarily an issue of the urban environment, specifically the blighted urban environment. Although feral cats can certainly exist in the wild by hunting, that does not appear to be their preferred habitat. In the wild, food becomes much more of a limiting factor for cats. Therefore, if we solve the problem of feral populations in the cities, we will have solved the great bulk of the overall problem. There are many people who argue that TNR is not the answer to the feral cat problem because we cannot possibly do TNR on enough feral cats to make a difference. Yes we can. We just need to concentrate on the areas where conditions exist that can maintain a large feral population, which means blighted urban environments. We do not need to do TNR on every feral cat in every jurisdiction in the United States to solve the problem, because in places where empty buildings and garbage are not available feral cat populations are likely to be self-limiting.

Second, we might want to see if we can coordinate TNR with programs to reduce urban blight. This will not only attack the problem at the roots, but it re-directs the public’s attention away from the feral cat “problem” and to the conditions from which the problem originates – the availability of empty structures and garbage. As an added benefit, attacking urban blight will reduce the rat population too. Simply removing cats from an urban area where they are thriving will likely result in a large increase in the rat population, since the same conditions favor both species. Coordinating blight-reduction measures with TNR could mean that colony caregiving must begin to include managed shelter as well as managed food sources.

Third, we need to confront bird conservationists with the implications of commensalism. As O’Connor discusses at length, birds are commensal species too. Some of the most successful commensal birds are pigeons, sparrows, and crows. Bird conservationists, oddly enough, are not interested in saving pigeons, sparrows, and crows from cat predation. In fact, they appear to hate the successful commensal birds as much as they hate cats. This is strong evidence that bird conservationists are more concerned about their view of “nature” than about animal welfare. Crows are among the most intelligent animals on the planet, yet bird conservationists tend to see them solely as pests. The idea that the life of an individual animal has value seems very foreign to the thinking of the typical bird conservationist.

Not all types of birds are commensal, and some live in the wild far from humans. These are often the rare species that bird conservationists love – not for themselves as individuals, of course, but because they represent that ideal, pristine version of nature that conservationists value. As far as I can tell, there have been few if any studies on feral cat presence in remote, wild regions of the United States like the swamps of Louisiana. I suspect that is because there are few feral cats in areas that are truly remote from human habitation. (The exception is on some oceanic islands where cats have been introduced and then the humans left, but that is a whole different story.)

So bird conservationists are barking up the wrong tree, so to speak, when they blame feral cats in the United States for killing the type of birds they care about. Since feral cats live primarily as scavengers in human settlements, the birds they kill are very likely to be the commensal species that bird conservationists hate anyway. Feral cat supporters need to press bird conservationists to be more specific about just what birds cats are killing. Are they killing bluebirds and goldfinches, or pigeons and sparrows? Is there decisive evidence that, in the United States, cats are a significant predator of rare bird species? And if such evidence is lacking, then they need to, in the immortal words of Trey Gowdy: “Shut up talking about things that you don’t know anything about.”

No Kill advocates, unlike bird conservationists, care about the lives of all animals, including starlings, pigeons, and crows. That is why we advocate for TNR, because managed cat colonies reduce whatever bird predation may exist (since managed colonies are provided with food) while also preserving the lives of the cats.

Feral cat advocates have some very strong arguments available to us in favor of TNR. We need to start pushing back harder on the bad science that bird conservationists have been rolling out to support their “kill cats” agenda. We need to stop trying to address their inadequate studies one by one and develop our own comprehensive picture of the relationship between cats and birds. One of the components of our picture should be that cats and birds co-exist extremely well in the suburbs (see my blog post about cats in the suburbs). Another should be that cats in urban areas, to the extent that they are preying on birds at all, are likely preying on commensal bird species that are not endangered and that many people regard as pests. Another part of the picture should be that the cat, since it is a commensal animal, is a highly unlikely predator of the rare bird species that live in areas remote from human habitation. And the final piece of the puzzle is that since cats are commensal, TNR can work to control populations where control is needed most.

Bird conservationists have for the most part been getting a free ride with their simplistic claim that “cats kill birds, therefore cats are bad for bird populations.” They have even had the cheek to ask the taxpayers to fund their “kill cats” programs. Feral cat advocates have been slow to push back on the science because we, for the most part, are not scientists. That needs to change. As Bob Dylan said: “You don’t need a weatherman to know which way the wind blows.”

14 thoughts on “The Commensal Cat

  1. Kim Bartlett

    Thanks for this article, which makes the excellent point that TNR efforts should “concentrate on the areas where conditions exist that can maintain a large feral population,” and not prioritize areas where feral cat populations are likely to be self-limiting because of reduced shelter and garbage. An important error is made, however, in claiming that rare bird species live in “areas remote from human habitation.” There is not much territory in the continental U.S. that is exists so far from a restaurant, gas station, and motel complex that a few cats won’t have taken up residence under a dumpster. Even a species that tends to live in remote areas will still, from time to time, be seen at the edge of its habitat, where pet or feral cats may lurk, or the species may be migratory, putting the birds at risk of predation from cats along its flyways. I support TNR, but with the provision that cats will only be returned to sites where they will be relatively safe and, above all, where their presence is tolerated. This excludes maintaining feral cat colonies in or along the edges of territory designated as wildlife habitat.

  2. Susan Houser Post author

    I would guess that it is pretty rare for anyone to want to put a feral cat colony in or on the edges of a true wilderness, simply because true wilderness is not a very good, or a very common, habitat for domestic cats. What I have seen several times is cities refusing to consider TNR because there is “wildlife habitat” outside the city. Tallahassee is one example where this happened. Unfortunately, with bird conservationists, if you give them an inch they take a mile.

  3. Al-Hajj Frederick H Minshall

    Not a birder, but a ‘herper’. And ‘fisher’ (fisheries biologist) by trade. And you’re merely taking the ‘bird vs cat’ fallacy one step further by mischaracterizing it as a ‘commensal’ vs ‘wild’ fallacy. And you’re wrong again. It is an ‘invasive’ vs ‘native’ dichotomy, and it encompasses very valid concerns.

    Example. Introduction of invasive bullfrogs and African clawed frogs have devastated native frog populations in the western US–in some cases being the primary factor in reducing native frog ranges by as much as 75%.

    Remember Mark Twain’s famous “Jumping Frogs of Calaveras County”? Those were California red-legged frogs. They’re extinct in that county now because bullfrogs ate ’em all.

    So tell me, Ms. Houser–where does this fall on your ‘commensal vs wild’ spectrum? The invasive and native species involved are all frogs.

    Perhaps you should stick to lawyeriing and leave natural science to the biologists. Just sayin’

  4. Susan Houser Post author

    Gosh, my paltry bachelor’s in zoology pales before the awesomeness of your PhD – or whatever. But be careful, because if you condescend much further you will scrape your knees. As far as the spectrum from wild to commensal, it isn’t “mine.” You might want to take it up with Dr. Terry O’Connor. And as to your implication that I cannot report on such matters because I am a lawyer by profession, one thing I learned in my liberal education is that if you want to be taken seriously don’t rely on ad-hominem arguments.

  5. Al-Hajj Frederick H Minshall

    And deflection doesn’t work very well, either. The point of the argument is that it doesn’t fit in your manufactured dichotomy, and whoever you claim deserves credit for it is quite irrelevant. The real dichotomy is naturally-occurring species assemblages vs. those introduced by human agency. You still haven’t responded to that, because you prefer to misrepresent the question. Technically not ‘ad-hominem’. I’m criticizing your facetious argument, not you personally.

  6. Susan Houser Post author

    Not sure what you’re getting at here – that the commensal-wild distinction is not real? Good luck with that, it’s a far-out argument. Or are you arguing that if a species is “invasive” then all other characteristics about it are irrelevant? Again, good luck with that. I’m curious – exactly how would you define an “invasive” species? Were dogs “introduced by human agency”? Should they be wiped out along with cats? What about animals that migrate without human agency but then take over and kill existing species. Are they invasive? If not, then why not, when the outcome is exactly the same? I see a lack of rigor in the way the term “invasive” is used – not just by you, but in general. Surely you are aware that scientists who are in the pantheon of those who have PhDs have questioned both the subjectivity and the lack of rigor in the use of the term “invasive.” And — the overarching question here, which neither you nor any of your exalted cohort have answered, is — what is your plan to deal with feral cats, how are you going to pay for it, can you realistically expect buy-in from the public, and what is your evidence that it will succeed?

  7. Al-Hajj Frederick H Minshall

    I didn’t say it wasn’t real. I said it wasn’t relevant to this issue. If it was, you’d be remiss for not advocating TNR for rats and mice. IIRC you admit they’re ‘commensal’ as well. And are you arguing that invasive species are not deleterious to naturally-occurring fauna assemblages? Do you argue that dogs have not proven destructive when released into ecosystems where they did not naturally occur? I think most New Zealanders would disagree with you on that. BTW, do you have an example of a species migrating under its own power into a novel area and eradicating another species? Do tell. I’ve already partially answered your challenge on your other thread, and will do so in more detail. Just would rather you didn’t skip over what you’ve so far failed to answer in this discussion before moving onto that.

  8. Susan Houser Post author

    So, if I understand you, you are saying that “invasive species” should be defined as species that are introduced by humans and are harmful to native fauna. If that is the case, then it seems to me that the natural implication of your argument is that we should wipe out humans, or at least keep them from traveling to or living in the areas you want to keep pristine. Take the Galapagos Islands. Is it really possible to keep all “invasive” species off those islands in spite of the constant stream of tourists coming and going, with their ships and their luggage and their supplies, and the luggage and supplies of all the people who serve the tourists? And let’s say we were able to wipe out all the starlings in the USA (I assume you want them gone, since they may be the mother of all invasive species). How long would it be before someone re-introduced them? Are we also going to kill all the rats, mice, snakeheads, crows, kudzu, zebra mussels, grey squirrels, rabbits, African bees, Asian carp, and on and on? And how are we going to keep them from being re-introduced? Please tell me more.

  9. Al-Hajj Frederick H Minshall

    I’m saying that when a problem exists, there are at least two possible responses:

    (1) We can shrug our shoulders and say, ‘No point doing anything about it, because the problem will simply reassert itself in the future’, or

    (2) We can attempt to resolve it.

    You seem to advocate (1). I advocate (2). Hope this doesn’t take up too much space.

  10. Gina october

    Well said Susan. I have been saying for years, where are these so called bird conservationist when the bulldozers destroy worded lot after wooded lot, trampling the baby birds stuck in their nests, laying half alive and broken as the massive destructive machine buries them alive? Why aren’t they climbing those trees and relocating those nests if they are so damn concerned about dwindling bird populations? The cruelty alone of parent birds having to watch in horror, completely helpless as entire generations of birds are killed for profit and gain. Why aren’t the bird conservationist petitioning for the mass destruction of bulldozers and the people that pay and benefit from destroying the birds’ habitant ? And as Susan pointed out more eloquently and diplomatic than I, bird conservationist never seem to care about the lives of the birds thriving and surviving our constantly changing landscape. As we continue to destroy nature and our environment, not all species will survive along with us. They thrived in a particular environment that provided for their specific needs but only far as long as that environment remained unchanged.

  11. Al-Hajj Frederick H Minshall

    I will, despite this site’s ongoing censorship, attempt to reply point-by-point. You said:

    “Well said Susan. I have been saying for years, where are these so called bird conservationist when the bulldozers destroy worded lot after wooded lot, trampling the baby birds stuck in their nests, laying half alive and broken as the massive destructive machine buries them alive? Why aren’t they climbing those trees and relocating those nests if they are so damn concerned about dwindling bird populations?”

    Primarily because it wouldn’t do any good. Disturb and/or remove nests or handle nestlings, most parents abandon them. And again, you mischaracterize this as conflict between ‘cat-lovers’ and ‘bird lovers.’ It’s nothing of the kind.

    Your other fallacy is assuming that those who oppose proliferation of unrestrained feral and domestic cats are ignoring other issues such as habitat destruction. In fact, those of us concerned with conservation usually started out opposing habitat loss, wildlife mismanagement and other forms of human-engendered damage to wildlife communities long before we became aware of the egregious destruction inflicted by unrestrained, invasive felines.

    Point is proliferation of feral cats has proved more damaging than most other deleterious human activities except for outright habitat loss. We’re not opposed to feral cat proliferation and its resulting destruction to wildlife despite these other issues, but because of them.

    “The cruelty alone of parent birds having to watch in horror, completely helpless as entire generations of birds are killed for profit and gain.”

    Ethan Watters provided a better response to the above than I ever could in his well-written article “We Aren’t the World”:

    “Given that people living in WEIRD [western, educated, industrialized, rich, democratic] societies don’t routinely encounter or interact with animals other than humans or PETS, it’s not surprising that they end up with a rather cartoonish understanding of the natural world. “Indeed”… “studying the cognitive development of folk-biology in urban children would seem the equivalent of studying ‘normal’ physical growth in malnourished children.”

    –Pacific Standard, 25 Feb 2013 (emphasis mine)

    “Why aren’t the bird conservationist petitioning for the mass destruction of bulldozers and the people that pay and benefit from destroying the birds’ habitant?”

    Why don’t you stop using false equivalencies as if they constituted logical debate of this issue?

    “And as Susan pointed out more eloquently and diplomatic than I, bird conservationist never seem to care about the lives of the birds thriving and surviving our constantly changing landscape. As we continue to destroy nature and our environment, not all species will survive along with us. They thrived in a particular environment that provided for their specific needs but only far as long as that environment remained unchanged.”

    And one of the most destructive changes is introduction of invasive species by human agency:

    (1) There were once millions of American chestnut trees in the eastern US–they were nearly as big as California redwoods and comprised 25% of the original forests covering the eastern half of this continent. Only about a hundred remain in southeast Canada. They were nearly exterminated by introduction of the European sac fungus that causes Dutch elm disease (or chestnut blight), brought into North America by Europeans on trees imported from the Old World for ‘ornamental’ purposes. Their loss was ecologically catastrophic to eastern North America, and they’re but one of SEVERAL native tree species all but destroyed by the blight.

    (2) Although I’m all for Alaska in most respects, it’s undeniable that the state of Texas boasts the most diverse assemblages of plants and animals of any state in the union, many of which are found nowhere else. To try and save these unique biological communities from being uprooted and consumed by foraging feral swine, Texas Fish & Wildlife has declared unlimited open season on them. They’re not bothering with ‘TNR’ to try and control them.

    (3) Most of California’s native frog species are critically endangered, thanks to introduction of bullfrogs from east of the Rocky Mountains in 1905 for food, as well as from the later introduction of African clawed frogs, once a widely-used laboratory research animal. Both prey directly on native species, and both are vectors of Batrachochytrium dendrobatidis, a predatory fungus that has caused amphibian extinctions around the world and is now recognized as the worst recorded infectious epidemic among vertebrates ever recorded. And we have it here, thanks to irresponsible introduction of two invasive vectors.

    Unfortunately I could go on and on, but I hope this will make it clear that it never was merely a question of ‘cats vs. birds.’ It’s a question of invasive vs. native species, and of the need to preserve the latter. Favoring and invasive, disease-carrying predator over the needs–the very LIVES–of naturally-occurring animal species simply because the former are ‘cute and appealing’ is the height of irresponsibility and absolutely unjustifiable.

  12. Susan Houser Post author

    Just a quick response to your charge that I’m “censoring” comments. I’ve posted probably 90% of your comments, and the ones that I have not posted have been repetitive or for other reasons have not contributed to the debate. In numbers you’ve certainly had more posted comments than anyone else in this TNR debate, so I hardly think you have grounds to complain.

  13. Bill

    Gina, you assume that habitat loss and the impact of outdoor and feral cats on bird populations are both mutually exclusive. They are not. Habitat Loss AND feral and outdoor cats both tremendously impact native bird populations. This is fact and not up for debate. I’ve been to several zoning board meetings to discuss the impact of habitat loss, in particular in my area when a local township proposed the development of 30 new soccer fields in an area rich with migratory birds. Guess what, the soccer fields went in and the number of migratory birds in the area steeply declined.

    Now, ask yourself a simple question. Is it easier to reduce human population growth and proliferation which is a direct result of habitat loss, or is it easier to educate people about the responsibilities of proper pet ownership and need for removal of invasive, feral animals? Pretty obvious answer. We can immediately make an impact on native birds population declines just by keeping our cats inside and removing feral colonies.

    As a true “Animal Lover” I take all threats to biodiversity seriously, including the cute and furry ones. For millions of years prior to the arrival of civilized man in the western hemisphere, our native birds and mammals developed a very delicate predator/prey relationship. For millions of years our native birds and mammals were able to keep rodent populations in check. Yet, a mere 600 years ago civilized man arrived with his bio-engineered domestic animals, including Felis Catus. An animal that does not occur naturally in any environment and pound-for-pound is probably one of the most effective and prolific hunters on the planet. You see, feral cats are a man made problem that requires a man made solution. As other, very well thought out and educated responses have asked, do you advocate for TNR of feral pigs, feral pythons or any other invasive, feral animal? I don’t need your cat to take care of my rodent population. The single most effective rodent killer on the planet is a Barn Owl, an animal who actually relies on these mice for food and survival. And I certainly don’t need your cat defecating in my garden or spreading T. Gondii or Rabies or Plague.

    For the same reason we have leash laws for dogs, another bio-engineered, invasive species, we also need leash laws for Cats. Cats and Wildlife don’t mix. If you support Trap-Neuter-Re-Abandon and/or allow your cats to roam free you are directly responsible for destroying nature and our environment. And based on your comments I’m not even sure you care.

  14. Pingback: Feral Cat debate: Trap-Neuter-Return Is Sound Public Policy – National Geographic Society (blogs)

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