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The Unnatural World of Killer House Cats

Posted by Richard Conniff on March 28, 2014

Adorable but deadly (Photo: Richard Conniff)

Adorable but deadly (Photo: Richard Conniff)

My latest for Takepart:

Earlier this week, I published an article in the New York Times remembering a cat I once owned and loved named Lucky. She was my last outdoor cat, partly because her own death was a bloody reminder of just how dangerous the outdoor life can be for the cats themselves: She died one night, torn to pieces by a bobcat, after 10 years of wandering freely around the neighborhood.

But she was also my last outdoor cat because I realized, after the fact, how deadly outdoor cats can be for wildlife: By letting Lucky wander freely, I had made it possible for her to kill hundreds of birds, mammals, reptiles, and amphibians over the years. While writing about wildlife and maintaining my own yard with wildlife in mind, I had unintentionally been stripping wildlife from the entire neighborhood.

Other cat owners are increasingly coming to the same grim realization—in part because of a federal study last year that added up the billions of animals killed by cats every year in the Lower 48 States. I argued in my article that outdoor cats will soon be as socially unacceptable as smoking in the office, or leaving dog poop on the sidewalk. The editors headlined it “The Evil of Outdoor Cats,” and it attracted widespread attention on the web, some of it angry. One reader commented that a better headline would have been “The Evil of Humans.”

A lot of readers misunderstood a central point I was trying to make about the dramatic decline in bird populations in this country, and about the loss of habitat. Readers commented correctly that the real menace to wildlife comes from suburban sprawl, agricultural intensification, logging, mining, industrial pollution, and climate change. But a lot of cat-owners seemed to think that was an argument for continuing to let their cats go outside to kill. “Whatever damage cats are doing,” a reader in Seattle commented, “it can only be a small fraction of the many human-caused threats to wildlife, in particular habitat destruction.” It was like arguing that, because there are wars going on out there, my little murders shouldn’t count.

In fact, killings by outdoor cats matter far more than they might in a healthier world. My basic argument was that there’s hardly any place left for birds and other wildlife to live, and what habitat remains is often heavily fragmented. That makes animals far more vulnerable to predation by cats. Several readers who are scientists pointed out factors that actually make the effect of cat predation far worse than I had suspected.

The first is what biologists call “mesopredator release.” When humans remove wolves, coyotes, and other large predators from a habitat, the mid-size (or meso) predators they would otherwise kill or out-compete suddenly flourish. It’s boom time for skunks, raccoons, and especially house cats—which then go on to kill birds and other small animals in huge numbers.

Creating protected habitat, as that same Seattle reader suggested, doesn’t fix this problem. A 1999 study of mesopredator release looked at what happened when coyote populations declined and habitat became fragmented in southern California. The most important effect was indirect: The 46 percent of cat owners who sometimes kept their cats indoors because they didn’t want them to be eaten by coyotes no longer had to worry about that.

Around one habitat fragment in San Diego, 77 percent of neighboring cat owners let their cats wander outdoors—and almost all of those cats were killers. The math was devastating for wildlife: 35 cats from 100 nearby houses hunted in a 49-acre parcel of land. Some bird species hung on in that habitat with a few as 10 individuals. But the cats were bringing home 525 dead birds a year, and probably leaving many more tattered remains in the bush. Local extinctions were inevitable.

The other factor I failed to recognize was something biologists call “hyperpredation.” In a natural habitat, the predators tend to live by boom and bust. One year the foxes get fat because there are so many chipmunks to eat. The next year, there are too many foxes and too few chipmunks, and the foxes starve.   But pet cats, and colonies of feral cats, don’t live like that. We feed them, and we maintain them at densities many times higher than what’s normal for foxes or all other similarly-sized natural predators combined. When the chipmunks or sparrows go bust, the cats just go home for dinner. Then they come out again next day to hunt some more. It’s a miracle anything else manages to survive.

In the light of what I have learned from readers, I am beginning to think it’s time to re-name the popular practice of trying to control feral cat populations with TNR—that is, by trapping them, neutering them, and then releasing them again into the wild. A better name might be TNRH, for “Trap, Neuter, Release, and Hyperpredate.”

But let’s save that hot topic for another column.

14 Responses to “The Unnatural World of Killer House Cats”

  1. Woodsman, don’t your dare. Hush!

  2. great article. So important to tell this story . In New Zealand, house cats significantly contributed to 11 bird extinctions and are currently a direct threat to the survival of dozens more of our endangered lizards and birds.

  3. Birder said

    Great article. I do take issue here though…

    “Readers commented correctly that the real menace to wildlife comes from suburban sprawl, agricultural intensification, logging, mining, industrial pollution, and climate change.”

    The word ‘real’ bugs me. Readers are not commenting correctly that the ‘real’ menace to wildlife are those sources of mortality. All sources are real and deserve attention, whether climate change or loss of habitat, or anthropogenic causes including but not limited to pesticides, window strikes, communication towers, wind farms, and yes, cats. Humans permit pets to roam, humans dump unwanted animals. Humans re-abandon cats through TNR.

  4. Ted Williams said

    Very well said Dick. Unless we allow managers to control feral cats with poisons the way the Aussies do it the battle is lost. Trap, Neuter and Re-Abandon is crueler than any poison. See:

    http://archive.audubonmagazine.org/incite/incite0909.html

    • Walter Lamb said

      The effort to education cat owners to keep their pet cats indoors makes a great deal of sense, and I wish that ABC’s cats indoors program focused more on that educational effort. As with anything, however, we are always better served when we understand the complexities of a situation and strive for flexible (within reason) policies that maximize the results we are trying to achieve. From a conservation standpoint, that metric should be fewer cats in the environment. A lot of cat advocates would like that metric to be the number of cats spared from destruction in shelters, but as Bob Sallinger of Portland Audubon has noted, that is not a legitimate conservation metric. If we agree that the goal is to reduce cats in the environment, then we should agree that any policy that unwittingly leads to more cats in the environment is not an environmentally sound policy. So the question we ought to ask is what is the relative return on a dollar spent trying to pass outright bans on outdoor cats (or bans on TNR) versus the return on a dollar spent on education. It is certainly possible that a campaign to ban outdoor cats could also have an educational impact, but it is also possible that such a campaign might alienate pet owners and make them less receptive to the educational message. The point being, we have to cool off enough to the point where we can rationally consider these types of calculations, and not be scared to raise them for fear of branding by purists.

      On another post, Ted Williams took exception to my revisiting an episode that he clearly regrets. My intent was not to reopen an old wound, but to put into context arguments being made in the present. We all make mistakes, and I do believe that Ted’s general body of work has been beneficial to the cause of environmental conservation. I bring this up in this post because I think that Ted’s “ecological illiterate” label has some bearing when it comes to pet owners who are oblivious to the natural world. It is worth noting that there are millions of such folks, and they dwarf the number of people who are practicing any kind of control effort, whether lethal or non-lethal. I do get angry that such “ecological illiterates” do things like not sterilizing their pet cats, thinking that their cat having kittens is a great way to teach their kids about the cycle of life, etc. I also get angry that “ecological illiterates” purchase vehicles and homes that are far bigger than what they need, that they don’t recycle, that they litter cigarette butts because they wrongly think they are biodegardable, etc. All of these things make me angry and I am not immune from the occasional rant. However, we have to be cautious about rant-based policy recommendations. That was the point I was trying to make, perhaps insensitively, when I suggested that Ted was driven by anger and not by reason.

      When we argue that the answer to feral cat control is shooting by rifle or death by poison (whether naming the brand or not) we should be prepared to defend those policy proscriptions. Can we really make a dent in the population of outdoor cats, many of which live in urban and suburban areas, by shooting them with rifles? And if poison can only be administered by professionals in a way that does not endanger other animals, including people, then how effective do we expect it to be? Ted argued that acetaminophen is only harmful to cats, and that is simply incorrect. It is especially toxic to cats, but not uniquely toxic to cats, and anyone who disagrees could experiment on themselves by surpassing the recommended dosage (do not actually do this). I reject the idea that we should suppress legitimate criticism of an idea out of fear of hurting someone’s feelings or being labeled by others as being either cat lover or cat hater or anything else.

      I just read an interesting article in Scientific American that early Calculus was attacked by several mathematicians because it threatened the Orthodoxy of Jesuit beliefs. It is very easy for issues of ideology and morality to make their way into scientific discourse and we have to resist the temptation to treat science as a rivalry of opposing teams, as we have with this topic.

      Ted – I hope this puts my earlier comments in better context. If you are ever in Los Angeles, I would be happy to show you around our many wonderful bird watching spots. I will also show you the degraded but restorable upland habitat in our state ecological reserve in which the Department of Fish and Wildlife and the Annenberg Foundation want to construct a 46,000 sq ft “urban ecology center” that was originally named the “Wallis Annenberg Companion Animal Center.” I am confident that learning about this project will give new meaning to the term “ecological illiterate.”

      Walter

  5. rboschen3 said

    Reblogged this on rboschen3 and commented:
    Cats are the worst “invasive species” we have, FAR more damaging than any reptile or a python species barely holding on it the southern tip of Florida, yet totally unregulated. I hope folks remember this when they see laws being shoved down the throats of responsible reptile keepers.

  6. rboschen3 said

    Cats are the worst “invasive species” we have, FAR more damaging than any reptile or a python species barely holding on it the southern tip of Florida, yet totally unregulated. I hope folks remember this when they see laws being shoved down the throats of responsible reptile keepers.

  7. Sue.d said

    Food for thought. Situations vary so much. I don’t think all outdoor cats should be lumped together. Personally I am quite happy that my outdoor cat kills lots of mice. No one ever seems to mention that…. Where would we be without cats killing small rodents? Birds are not stupid, we just need to stop killing their habitat.

    • Birder said

      Sue, any outdoor cat has the potential to kill. The hunting instinct is separate from the urge to eat. A single cat can extirpate native fauna from a given site. Is that a risk you are willing to take? How do you know which mice and rodents your cat is killing? Are they native? Any rodent outdoors could have been a meal for a native predator like a hawk and not wasted as a chew toy. Utilizing cats for ‘rodent control’ is akin to using pesticides. Non target species are affected. Cats are indiscriminate killers. They kill rare, common, threatened, endangered, young, old, ill, healthy – essentially anything small that moves.

      This is not about the ‘intelligence’ of birds. This is about an introduced predator that didn’t evolve alongside native wildlife. To quote Richard Stallcup (20 years ago at least), “the out of control population of the domestic cat is vastly larger than all native predators combined”. Today, free-roaming cats are the single greatest direct human cause of bird mortality.

      This is not just about preserving habitat. Heart disease is the number one killer of women. So if you get breast cancer, are you going to ignore it?

      Be a responsible pet owner. If you want your feline to enjoy the outdoors and a window isn’t good enough, then go outside and supervise her, or take her on a lead, or build a catio. There are so many options. There is no need to inflict your cat on the local fauna.

    • Maja said

      Sue. Your cat could be killing birds and leaving them where they struggled, and only bringing you home mice (does she see that makes you happy?).

      Cats eating mice in your own house or barn would be fine, but it does mean there are fewer for any barn owls that might want those small meals, as do free-roaming cats stealing food from those creatures such as snakes which EVOLVED here – cats did not.

      BTW, I was told years ago by Chicago’s Animal Control that cats are not effective predators of rats.

      Meanwhile there’s the problem of cats using the neighbors’ gardens as litterboxes. Their excrement stinks and is not good manure like that of horses and other herbivores.

      Also cats allowed to roam can pick up and then spread diseases and pathogens such as Toxoplasmosis gondii, which sexually reproduces only in felines and which has now been found in sea otters and whales. These native creatures did not ask for humans to inflict Toxo on them, but which cat people ARE in fact inflicting on all Nature.

      Toxo has now been implicated in schizophrenia and bipolar disorder. A Danish study found that of women who were depressed, those with Toxo were four times more likely to attempt suicide, used lethal means more often, and were morel likely to succeed.

  8. […] https://strangebehaviors.wordpress.com/2014/03/28/the-unnatural-world-of-killer-house-cats/ […]

  9. […] cats are  major bird killers. In many cities, one attempt to control the problem, called “Trap-Neuter-Return,” or TNR, has […]

  10. […] The Unnatural World of Killer House Cats […]

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