A Critical Assessment of “Critical Assessment”—Part 1

The first in a series of posts that breaks down my critique of the essay “Critical Assessment of Claims Regarding Management of Feral Cats by Trap-Neuter-Return” (Conservation Biology, Volume 23, No. 4, 887–894) by Travis Longcore, Catherine Rich, and Lauren M. Sullivan.

How many birds are killed by cats? It’s a fair question. And if Longcore et al. are to be believed, we actually have a pretty good handle on this issue:

Feral and free-roaming cats are efficient predators, and their abundance results in substantial annual mortality of wildlife. Churcher and Lawton (1987) concluded that cats were responsible for 30% of the mortality of House Sparrows (Passer domesticus) in an English village. May (1988) extrapolated their results to an estimated 100 million birds and small mammals killed per year in England. Although this extrapolation is often criticized for the limited geographic scope and number of cats studied, Woods et al. (2003) confirmed and refined this result with a larger sample size and geographic area that included England, Scotland, and Wales. From a survey of cat owners that documented prey returned by 696 cats, Woods et al. (2003) estimated that the 9 million cats in Britain kill at least 52–63 million mammals, 25–29 million birds, and 4–6 million reptiles each summer. In North America Coleman and Temple (1996) developed estimates of cat densities in Wisconsin and associated mortality of 8–217 million birds per year.

The relationship between cat predation and bird populations is highly complex, and our understanding quite limited—something Longcore et al. only hint at. It doesn’t help matters that results of small, isolated studies are often extrapolated from rural to urban environments, from one region to another, and so forth. In 1995, Churcher himself cautioned against making such leaps: “I’d be very wary about extrapolating our results even for the rest of Britain, let alone America,” he told Catnip, a newsletter published by the Cummings School of Veterinary Medicine at Tufts University.

Actually, Churcher went much further: “I don’t really go along with the idea of cats being a threat to wildlife. If the cats weren’t there, something else would be killing the sparrows or otherwise preventing them from breeding.” [1] Although Longcore et al. seem eager to cite Churcher and Lawton’s now-classic work as “evidence” of the damage cats can do, they make no mention of Churcher’s later comments (just one of many examples of their tendency to “cherry pick” from the literature only the bits and pieces that fit neatly into their argument).

But back to the number of birds killed by cats. Many of the studies on the subject—including those cited by Longcore et al.—are quite flawed. Among the numerous issues that call into question their estimates are assumptions regarding the number of cats that actually hunt, the number of cats allowed outdoors, the number of cats that live in a particular area, and so forth. And then, of course, there are the risks inherent in estimating population numbers and characteristics based on a small sample size.

(In fact, Woods et al. go to some lengths to emphasize the limitations of their study, conceding, for example, that they “may have focused on predatory cats.” [2] This is just one of many reasons the authors cite for requesting that their work be treated “with requisite caution”—a request apparently ignored by Longcore et al.)

By referring uncritically to such studies, Longcore et al. give far greater importance to this work than is warranted. Repeating—and therefore reinforcing—figures known to be erroneous and/or misleading is simply irresponsible.

The fact that the “English village” study and “Wisconsin Study” have been so thoroughly discredited (see, for example, the comments of Nathan Winograd, director of the No Kill Advocacy Center, and a report by Laurie D. Goldstein, Christine L. O’Keefe, and Heidi L. Bickel) raises some unsettling questions about their inclusion in a paper billed as a “critical assessment.” For example: Are the authors interested enough in rigorous scientific inquiry to look beyond “the usual suspects” in their assessment of the key issues?

One might also wonder: Given the important literature that Longcore et al. choose to overlook, ignore, or dismiss (to be addressed in detail in future posts), what is their motivation for writing the essay in the first place? Actually, this question was answered in January, two months after the paper’s publication, when L.A. Superior Court Judge Thomas McKnew decided in favor of an injunction against publicly supported TNR in Los Angeles (LASC BS115483). The Urban Wildlands Group (for which Longcore serves as Science Director, and Rich as Executive Officer) was the lead petitioner in the case.

If “Critical Assessment” is any indication, the case had much more to do with politics, PR, and marketing than with science.

1. n.a. (1995). What the Cat Dragged In. Catnip, 4–6.

2. Woods, M., Mcdonald, R. A., & Harris, S. (2003). Predation of wildlife by domestic cats Felis catus in Great Britain. Mammal Review, 33(2), 174-188.

Works cited in “Critical Assessment” excerpt:

• Churcher, P. B., & Lawton, J. H. (1987). Predation by domestic cats in an English village. Journal of Zoology, 212(3), 439-455.
• Coleman, J. S., & Temple, S. A. (1996). On the Prowl. Wisconsin Natural Resources, 20, 4–8.
• May, R. M. (1988). Control of feline delinquency. Nature, 332, 392-393.

The Things People Say (or Don’t)—Part 3

The American Bird Conservancy (ABC) is among the most visible organizations to oppose TNR—and put PR ahead of the relevant science (which ABC has been doing for years now).

ABC was one (along with the L.A. Audubon Society and Urban Wildlands Group) of several petitioners in the case that eventually led to an injunction against publicly supported TNR in Los Angeles. Following the court’s decision, ABC’s Senior Policy Advisor, Steve Holmer, told the Los Angeles Times:

The latest estimates are that there are about . . . 160 million feral cats [nationwide]… It’s conservatively estimated that they kill about 500 million birds a year.

Days later, I sent Holmer an e-mail, asking for details about his figure of 160 million feral cats (the number of birds killed could, I assumed, be addressed later). To his credit—and unlike the people I tried to contact at the Urban Wildlands Group and L.A. Audubon Society—Holmer actually replied, leading to a cordial but brief correspondence in which he directed me to the work of Nico Dauphiné and Robert J. Cooper.

Sure enough, just two pages into Dauphiné and Cooper’s article [1] (available for download via the ABC website):

There is therefore an estimated total of 117–157 million free-ranging cats in the United States.

But there are a number of significant problems with their estimate—which is calculated by combining an estimated number of feral cats with an estimated number of owned cats having outdoor access. Here, in a nutshell, is a breakdown of their calculation:

Dauphiné and Cooper start with 60–100 million “stray and feral (unsocialized) cats, nearly all of which range freely outdoors” a figure taken from a 2004 paper by David Jessup [2]. But, because Jessup didn’t cite his source(s), this is actually no estimate at all. At best, it’s a guess—and one intended to paint as stark a picture as possible.

Then, citing a 2004 paper (which in turn cites a study commissioned by ABC—the results of which are summarized here) by ABC’s Linda Winter [3], Dauphiné and Cooper suggest that “approximately 65%” of pet cats “are free-ranging outdoor cats for at least some portion of the day.” Taking 65% of 88 million—the number of pets cats estimated by the American Pet Products Association’s 2008 National Pet Owners Survey—the authors arrive at 57 million pet cats with outdoor access.

But what does that mean, to be free-ranging for at least some part of the day?

A 2003 survey conducted by Clancy, Moore, and Bertone [4] suggested that nearly half of the cats with outdoor access were outside for two or fewer hours a day. And 29% were outdoors for less than an hour each day. And a closer look at the study commissioned by ABC  indicates similar behavior: “35% keep their cats indoors all of the time” and “31% keep them indoors mostly with some outside access.” [5]

For Dauphiné and Cooper, though, these cats are no different from feral cats. For them to simply add the number of “part-time” outdoor cats to the population of “free-ranging outdoor cats” is highly misleading! The authors have no idea what impact these cats might have on bird populations—which is the stated purpose of their paper.

Note: For a closer look at the flaws in Dauphiné and Cooper’s paper, download “One Million Birds,” by Laurie D. Goldstein.

*     *     *

OK, back to Steve Holmer and the L.A. Times

Holmer’s estimate of 160 million is not a range, but the high limit of a seriously-flawed estimate (which is itself based on little more than wild guesses). And he refers specifically to feral cats—an error even Jessup, Dauphiné, and Cooper (none of whom, it seems, is likely to give feral cats even the slightest benefit of the doubt) don’t make.

Given the context of the discussion—TNR in Los Angeles—such an error was likely (perhaps intended?) to have serious consequences. To suggest that there are 160 million feral cats in this country—approximately one feral cat for every two human inhabitants—is irresponsible and manipulative. And it raises doubts about the integrity of ABC and its representatives. All of which I told Holmer. His reply read, in part:

We are doing are [sic] best to convey the facts as they become available. The 160 million figure was based on an earlier version of Nico’s latest paper and are now being updated in our materials which should now say:

There are currently 88 million pet cats in the U.S. according to a pet trade association, and that number is growing. In addition, it is estimated that there may be 60–100 million free-ranging feral cats in the U.S., and that these cats may collectively kill more than one million birds each day. Reducing this mortality even a small amount could potentially save millions of birds each year.

I haven’t checked the ABC website to verify Holmer’s claim. In any event, the damage was already done; ABC and the other petitioners had put a stop to publicly supported TNR in Los Angeles. And, from what I’ve seen (I’ve yet to wade through the thousands of pages of discovery documents in the case), they’d done so by selectively overlooking, ignoring, and misrepresenting the scientific research. Or, in the case of Holmer’s comment to the Times, simply “inventing” it.

By the way, I asked Holmer about his revised figure of “more than one million birds each day” killed by cats. He’s stopped replying to my e-mail.

1. Dauphiné, N. and Cooper, R.J., Impacts of Free-ranging Domestic Cats (Felis catus) on birds in the United States: A review of recent research with conservation and management recommendations, in Fourth International Partners in Flight Conference: Tundra to Tropics. 2010. p. 205–219

2. Jessup, D. A. (2004). The welfare of feral cats and wildlife. Journal of the American Veterinary Medical Association, 225(9), 1377-1383.

3. Winter, L., “Trap-neuter-release programs: the reality and the impacts.” Journal of the American Veterinary Medical Association. 2004. 225(9): p. 1369-1376.

4. Clancy, E. A., Moore, A. S., & Bertone, E. R. (2003). Evaluation of cat and owner characteristics and their relationships to outdoor access of owned cats. Journal of the American Veterinary Medical Association, 222(11), 1541-1545.

5. ABC. (1997). Human Attitudes and Behavior Regarding Cats. Washington, DC: American Bird Conservancy. Available at: http://www.abcbirds.org/abcprograms/policy/cats/materials/attitude.pdf

The Things People Say (or Don’t)—Part 2

Like the Urban Wildlands Group, the Los Angeles Audubon Society seems eager to spread the word about the “threat” of feral cats. But, just like Urban Wildlands Group, what they’re saying doesn’t always add up.

The L.A. Audubon Society was (along with the Urban Wildlands Group) a petitioner in the case (LASC BS115483) that eventually led to an injunction against publicly supported TNR in Los Angeles. So it was no surprise to see a representative quoted in the Los Angeles Times:

“At San Pedro’s Cabrillo Beach, a feral cat colony resides near where snowy plovers nest, said Garry George, conservation chairman for the Los Angeles Audubon Society. At San Francisco’s Golden Gate Park, George said, feral cats have wiped out the California quail population. And in San Diego, feral cats roam free near a habitat for the California least tern, which officials are trying to monitor and protect, he said.”

I’ve yet to look into George’s claims—and will reserve judgment until I have. That said, I think there’s reason to be wary. In February 2009, George had an article published in the online version of Los Angeles Magazine that raises questions about his ability to serve as a trustworthy spokesperson on the subject of feral cats. In “How to Make Your Yard a Bird Magnet,” George writes:

If feral cats are destroying your property, including your birds, you can use a Hav-a-Heart trap with a permit from Animal Services. They will spay or neuter the cats you trap and offer to find them a home.

To start with, it’s not clear that George’s bit of advice (including a link taking readers to the American Bird Conservancy’s Cats Indoors! campaign, a topic all its own) belongs in the article all. Then there’s his choice of words (to hear George tell it, you’d think real estate values in L.A. would be suffering for all the destruction wrought by feral cats!).

The real issue, though, is George’s assertion that L.A. Animal Services will sterilize and help find homes for the feral cats you trap. I’ve spoken with a representative at L.A. Animal Services, and was told—in no uncertain terms—that this is simply not the case. And it wasn’t true when George wrote it, either.

It’s hardly surprising—given how overcrowded L.A.’s shelters are with adoptable cats—that they’re not offering to find homes for feral cats (which often make for “difficult” adoption candidates). For George to suggest that these cats were headed for a happy ending is highly irresponsible. Either he didn’t know any better, or he intended his statement to be misleading and deceptive (he failed to respond to my inquiries on the subject). In either case, George had no business writing what he did. The fact that he did write it raises unsettling questions about his integrity and that of the organization he represents.

All of which begs another rather unsettling question: Do supporters of the L.A. Audubon Society fully understand what they’re supporting?

The Things People Say (or Don’t)—Part 1

Wildlife/bird advocates opposed to TNR are eager to talk to the press, so why won’t they reply to my e-mail?

Just about the time I was writing my response to “Critical Assessment of Claims Regarding Management of Feral Cats by Trap-Neuter-Return” (Conservation Biology, Volume 23, No. 4, 887–894), its lead author, Travis Longcore, began showing up in the news. The Urban Wildlands Group, for which Longcore serves as science director, was the lead petitioner in the case that would eventually lead to an injunction against publicly supported TNR in Los Angeles.

Given the obvious bias and overall tone of Longcore’s paper, I was hardly surprised to read what he told the press. There’s this, for example, from an interview with Southern California Public Radio:

“Feral cats are documented predators of native wildlife,” said Travis Longcore, science director for the Urban Wildlands Group. “We do not support release of this non-native predator into our open spaces and neighborhoods, where they kill birds and other wildlife.”

Hardly the stuff of controversy, at least at first glance. Who can argue with the fact that cats kills birds and other wildlife? That’s what predators—including cats and a number of other species, too, of course—do. Nobody’s debating that. What impact this predation has on birds and wildlife is another matter altogether—one Longcore doesn’t address here. (I’ll be addressing this issue repeatedly in future posts, starting with a critique of Longcore’s essay in Conservation Biology).

What’s more interesting is Longcore’s reference to cats as “non-native” and wildlife as “native.” It’s a recurring theme in the feral cat debate: native is inherently good; non-native is inherently bad (even worse is invasive non-native, another term often used to demonize cats). Never mind the fact that the cats are here because we brought them here, or the hypocrisy of the native/non-native argument. We routinely protect non-native species from native predators—consider, for example, the current controversy over livestock and wolves. Again, a topic to delve into more deeply in the future.

A week later, Longcore was quoted in the Los Angeles Times:

“It’s ugly; it’s gotten very vicious,” said Travis Longcore of the Urban Wildlands Group, one of the organizations that sued the city on behalf of the birds. “It’s not like we’ve got a vendetta here. This is a real environmental issue, a real public health issue.”

No vendetta? Maybe not, but Longcore’s essay in Conservation Biology has an agenda that takes priority over the science (hardly surprising in retrospect—given the timing of its publication, it must have been written while Longcore was preparing for the L.A. case). His apparent concern for the environment and public health strike me as largely disingenuous.

Also from the Times:

Those cats, Longcore said, often are diseased. And when colonies are fed, the practice often attracts more cats, either from around the neighborhood or because people dump new cats.

Let’s set aside for the moment Longcore’s assertion about colonies attracting cats, feral or dumped (I’ll get to that in another post). What about his suggestion that “these cats are often diseased”? In his own paper, Longcore acknowledges a rate of only 5–12% overall for feline leukemia virus (FeLV) and/or feline immunodeficiency virus (FIV). In the largest of the studies he cites, more than 12,000 cats were tested for FeLV and FIV, revealing an overall rate of infection of 5.2%, which, noted the researchers, “is similar to results previously reported for feral cats and for pet cats.” [1]

What about rabies? According to the Centers for Disease Control and Prevention, “approximately 1% of cats… tested for rabies were found positive” in 2008, the last year for which statistics are available.

It’s difficult to see how these rates of infection would lead anybody to suggest that free-roaming cats are “often diseased.” And I don’t expect to get any clarification from Longcore. While he seems eager to talk to mainstream media, which accepts his claims at face value (and passes them along as accurate to the public), he has yet to respond to my e-mail inquires.

I realize that taking issue with Longcore’s comments will no doubt strike some people as nitpicking. But such statements—which put PR before science—only impede any honest discussion of the issues.

[1] Wallace, J. L., & Levy, J. K. (2006). Population characteristics of feral cats admitted to seven trap-neuter-return programs in the United States. Journal of Feline Medicine & Surgery, 8, 279–284.