Without Apologies

The conversation continues on Audubon magazine’s blog, The Perch, with Travis Longcore doing everything he can to dodge the straightforward question I posed: If TNR and the feeding of feral cats are outlawed, then what will become of the many, many cats no longer receiving human assistance?

Among the topics he prefers to discuss are—and I have to say, this one caught me by surprise—me. Especially my reference to him as a “great purveyor of misrepresentations and bias” on the Vox Felina Facebook page. OK, perhaps I could have worded that differently, but as I point out in my most recent reply (fourth comment, page 2), if he’s going to stand by his 2009 paper, then he really has earned the title.

In his reply to a post by Vox Felina reader Laurie G., of Stray Pet Advocacy, Longcore lays out a litany of complaints against me:

“Peter Wolf has been attacking scientists with demeaning generalizations and grossly inflammatory statements on his blog for months now. He can also be clever and I appreciate the exchange we’re having on this page, but he accuses scientists of being grossly in competent and corrupt on a regular basis (bordering on slander) so I’m not going to apologize for being critical of him. Given the level of rhetoric on his blog and his vox felina persona on FB directed at me, this [is] a comparatively civil discussion.”

I don’t know about “bordering on slander.” I try to keep my criticisms focused on specific aspects of specific studies, reports, reviews, etc. And I go out of my way not to make hasty generalizations. As for all the rest: guilty.

Meanwhile, over at The Wildlife Society blog, Making Tracks, my comment (asking Executive Director/CEO Michael Hutchins the same question I posed to Longcore) has yet to be approved despite repeated attempts on my end. Apparently, my last exchange with Hutchins was…. well, my last exchange.

Repeat After Me

Listening to NPR’s On the Media this weekend, I was struck by a story (first broadcast in 2006) about how certain “sticky” numbers—however dubious—find their way into the media landscape and beyond, as On the Media co-host Brooke Gladstone noted:

“Four years ago, we delved into the mysterious number, said to be 50,000, of child predators online at any given time. It was cited by the NBC Dateline program “To Catch a Predator” and also by then Attorney General Alberto Gonzales.

But spokespersons for the FBI, the National Center for Missing and Exploited Children, and the Crimes against Children Research Center said it was not based on any research they were aware of. The A.G.’s office at the time, well, they said it came from Dateline.”

Wall Street Journal columnist Carl Bialik, who spoke to Gladstone for the story, described the process whereby such slippery figures gain traction:

“An interesting phenomenon of these numbers is that they’ll often be cited to an agency or some government body, and then a study will pick it up, and then the press will repeat it from that study. And then once it appears in the press, public officials will repeat it again, and now it’s become an official number.”

All of which sounds very familiar—Bialik could easily be describing the “official numbers” put out by so many TNR opponents. Among those that have gained the most currency are the predation estimates from the Wisconsin Study, the American Bird Conservancy’s figure for the proportion of birds in the diets of free-roaming cats, and Dauphiné and Cooper’s estimate of free-roaming cats in the U.S.

The Wisconsin Study
Despite its having been discredited long ago (see, for example, “Addressing the Wisconsin Study”), the Wisconsin Study continues to be cited as if its estimate of 8–219 million birds killed by the state’s rural cats [1] was credible. As recently as last year, Longcore et al. cited the work in their essay “Critical Assessment of Claims Regarding Management of Feral Cats by Trap–Neuter–Return.” [2]

This, despite the fact that—15 years earlier—co-author Stanley Temple told the press:

“The media has had a field day with this since we started. Those figures were from our proposal. They aren’t actual data; that was just our projection to show how bad it might be.” [3]

It’s true: the media has had a field day. Among the major newspapers to cite the Wisconsin Study are the Wall Street Journal [4], the New York Times [5], and the Los Angeles Times [6]. However, as I’ve described previously, it’s been the wildlife conservationists and bird advocates who’ve really had a field day with the Wisconsin Study:

  • The American Bird Conservancy (ABC) refers to the study, in its brochure Domestic Cat Predation on Birds and Other Wildlife. And the ABC goes one step further, pointing out that Coleman and Temple’s estimate was for rural cats, and that “suburban and urban cats add to that toll.” [7]
  • A 2009 article in Audubon Magazine suggests “cats were annually knocking off somewhere in the neighborhood of 8 million birds just in rural Wisconsin.” [9] To the magazine’s credit, they used Coleman and Temple’s low estimate—but none of the numbers from the Wisconsin Study are scientifically sound.

Birds Represent 20–30% of the Diet of Free-roaming Cats
According to an ABC report (downloadable from their website), “extensive studies of the feeding habits of domestic, free-roaming cats… show that approximately… 20 to 30 percent [of their diet] are birds.”

This, apparently, is the same report that Ellen Perry Berkeley debunked in her book, TNR Past Present and Future: A history of the trap-neuter-return movement, noting that the ABC’s 20–30% figure was not based on “extensive studies” at all. [10] In fact, just three sources were used: the now-classic “English Village” study by Churcher and Lawton [11], the Wisconsin Study (described above), and Mike Fitzgerald’s contribution to “The Domestic Cat: The Biology of Its Behaviour.” [12]

This gets a little complicated, so bear with me.

When Churcher and Lawton reported, “overall, birds comprised 35% of the total catch,” [11] they were referring to prey tallies recorded by study participants—not to the overall diets of the cats involved. Figures obtained through similar methods for the Wisconsin Study were 20–23%, [1, 13, 14] which the authors suggest—citing Fitzgerald’s comprehensive review of predation and dietary studies—are in line with other work:

“Extensive studies of the feeding habits of free-ranging domestic cats over 50 years and four continents [12] indicate that small mammals make up approximately 70% of these cats’ prey while birds make up about 20%.” [14]

But they’re comparing apples and oranges. Both the English Village and Wisconsin Studies report the percentage of birds returned as a portion of the “total catch,” whereas Fitzgerald reports percentage by frequency (i.e., the occurrence of birds in the stomach contents or scats of free-roaming cats), a point apparently lost on Coleman and Craven. The 21% figure [12] they refer to, then, is simply not comparable to their own (or that of the English Village study, a fact Churcher and Lawton acknowledge in their paper). As Berkeley notes, “this would put birds, as a portion of the diet of cats, at roughly 7 to 10.5 percent—nowhere near the ‘20 to 30 percent’ figures unleashed on the unscientific public by ABC!”

To put all of this into more familiar terms, it’s a bit like saying that coffee makes up 20–30% of the American diet versus saying that 20–30% of Americans drink coffee each day.

Nevertheless, 13 years after the ABC first published its report, the myth persists. The report—including the mistaken dietary figures—is still available. And the National Audubon Society has helped perpetuate the error, noting in its Resolution Regarding Control and Management of Feral and Free-Ranging Domestic Cats:

“…it has been estimated that birds represent 20–30% of the prey of feral and free-ranging domestic cats.”

Estimates of Free-roaming Cats
In January, Steve Holmer, the ABC’s Senior Policy Advisor, told the Los Angeles Times, “The latest estimates are that there are about . . . 160 million feral cats [nationwide].” Sounds like an awful lot of cats—nearly one for every two humans in the country. So where does this figure come from?

The source is a paper by Nico Dauphiné and Robert Cooper (which can be downloaded via the ABC website), presented at the Fourth International Partners in Flight conference. In it, Dauphiné and Cooper use some remarkably creative accounting, beginning with an unsubstantiated estimate of unowned cats, to which they add an inflated number of owned cats that spend time outdoors. In the end, they conclude that there are “117–157 million free-ranging cats in the United States.” [15] (For a more thorough explanation, see my previous post on the subject.)

Estimating the number of free-roaming cats wasn’t even the point of their paper. As the title—“Impacts of Free-ranging Domestic Cats (Felis catus) On Birds In the United States: A Review of Recent Research with Conservation and Management Recommendations”—suggests, the primary purpose was to describe the cats’ impact on birds. The authors’ exaggerated figure was merely a convenient route to their estimate of birds killed annually by cats: “a minimum of one billion birds” [15] (which, it should be clear, has the potential to become a very sticky number).

Holmer goes a step further, using only the upper limit of the range published by Dauphiné and Cooper, and making the subtle—but important—shift from free-ranging to feral cats.

When I asked him about this, he explained that those figures were “based on an earlier version of Nico’s latest paper and are now being updated in our materials.” I don’t know that any such changes were made; and in any event, the bogus estimate has already been published in the L.A. Times—as if it were true.

*     *     *

TNR opponents will often point to the vast collection of research studies, government reports, news accounts, and the like, that support their assertions. Drill down a bit into that collection, though, and they all start to look alike: the same familiar sources, the same flawed studies—and the same bogus figures. These figures have become the kind of “official numbers” Bialik refers to: quantitative poseurs owing their popularity to tireless—and irresponsible—repetition more than anything else.

Literature Cited
1. Coleman, J.S. and Temple, S.A., On the Prowl, in Wisconsin Natural Resources. 1996, Wisconsin Department of Natural Resources: Madison, WI. p. 4–8. http://dnr.wi.gov/wnrmag/html/stories/1996/dec96/cats.htm

2. Longcore, T., Rich, C., and Sullivan, L.M., “Critical Assessment of Claims Regarding Management of Feral Cats by Trap–Neuter–Return.” Conservation Biology. 2009. 23(4): p. 887–894.

3. Elliott, J., The Accused, in The Sonoma County Independent. 1994. p. 1, 10.

4. Sterba, J.P., Tooth and Claw: Kill Kitty?, in Wall Street Journal. 2002: New York. p. A.1

5. Barcott, B., Kill the Cat That Kills the Bird?, in New York Times. 2007: New York. http://www.nytimes.com/2007/12/02/magazine/02cats-v–birds-t.html

6. Kennedy, J.M., Killer Among Us, in Los Angeles Times. 2003: Los Angeles. http://articles.latimes.com/2003/dec/23/news/os-cat23

7. ABC, Domestic Cat Predation on Birds and Other Wildlife. n.d., American Bird Conservancy: The Plains, VA. www.abcbirds.org/abcprograms/policy/cats/materials/predation.pdf

8. FWS, Migratory Bird Mortality. 2002, U.S. Fish and Wildlife Service: Arlington, VA. www.fws.gov/birds/mortality-fact-sheet.pdf

9. Williams, T., Felines Fatale, in Audubon Magazine. 2009, National Audubon Society: New York, NY. http://www.audubonmagazine.org/incite/incite0909.html

10. Berkeley, E.P., TNR Past present and future: A history of the trap-neuter-return movement. 2004, Bethesda, MD: Alley Cat Allies.

11. Churcher, P.B. and Lawton, J.H., “Predation by domestic cats in an English village.” Journal of Zoology. 1987. 212(3): p. 439-455.

12. Fitzgerald, B.M., Diet of domestic cats and their impact on prey populations, in The Domestic cat: The biology of its behaviour, D.C. Turner and P.P.G. Bateson, Editors. 1988, Cambridge University Press: Cambridge; New York. p. 123–147.

13. Coleman, J.S. and Temple, S.A., Effects of Free-Ranging Cats on Wildlife: A Progress Report, in Fourth Eastern Wildlife Damaage Control Conference. 1989: University of Nebraska—Lincoln. p. 8–12. http://digitalcommons.unl.edu/ewdcc4/7

14. Coleman, J.S., Temple, S.A., and Craven, S.R., Cats and Wildlife: A Conservation Dilemma. 1997, University of Wisconsin, Wildlife Extension. http://forestandwildlifeecology.wisc.edu/wl_extension/catfly3.htm

15. 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. 2009. p. 205–219.

A Critical Assessment of “Critical Assessment”—Part 2

The second 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.

Like so many others interested in blaming cats for declining bird populations, Longcore et al. refer to a 1996 article in Wisconsin Natural Resources magazine [1], in which the authors estimate that 8–219 million birds are killed annually by “free-ranging rural cats” in the state. More than any other work, the “Wisconsin Study” (which is actually a series of articles, the first being published in 1993 [2]) has been used as “evidence” against advocates for free-roaming cats in general, and TNR in particular.

In my previous post, I referred only briefly to Coleman and Temple’s work; in fact, careful scrutiny is in order. Among the study’s more notable flaws:

  • Its “estimate that 23 percent of [cats’] diet consists of birds” is well above the 7–10.5% figure suggested by Fitzgerald, [3] one of the world’s foremost experts on the subject (for a detailed account, see Ellen Perry Berkeley’s 2004 book, TNR Past present and future: A history of the trap-neuter-return movement [4]). In fact, Coleman and Temple cite Fitzgerald’s work, making the error all the more egregious.
  • Coleman and Temple assume that all cats hunt; in fact, it has been suggested that only 35–56% of cats are hunters. [5,6]
  • Their figures for cat density, too, have been challenged. [7]

For a more complete critique of the Wisconsin Study, download the 2003 report by Laurie D. Goldstein, Christine L. O’Keefe, and Heidi L. Bickel at Stray Pet Advocacy.

Now 14 years old, the Wisconsin Study has achieved mythical status—but not in a good way. I suppose it’s because the numbers are so impressive. Forget the fact that they’re essentially fictitious—they’re simply too tempting for people who see cats as the primary reason for declining bird populations. James Tantillo, a Lecturer in the Department of Natural Resources at Cornell University’s College of Agriculture and Life Sciences, is right on the money when he refers to Coleman and Temple’s estimate as an example of a “‘mutant statistic’ whose origins and genesis have been greatly lost to the people who cite it.” [8]

*     *     *

Among those who cite it are, of course, Longcore et al. But they failed to cite an important follow-up comment by one of the authors of the Wisconsin Study. In a 1994 interview, an “exasperated” Temple told The Sonoma County Independent:

The media has had a field day with this since we started. Those figures were from our proposal. They aren’t actual data; that was just our projection to show how bad it might be. [9]

More than the media, however, it’s been the wildlife conservationists and bird advocates who have had a field day with the Wisconsin Study. Here are just a few examples:

  • The American Bird Conservancy refers to the study in its brochure Domestic Cat Predation on Birds and Other Wildlife. But ABC goes one step further, pointing out that Coleman and Temple’s estimate was for rural cats, and that “suburban and urban cats add to that toll.” [10]
  • The U.S. Fish and Wildlife Service cites the study’s “intermediate” estimate of 39 million birds in its Migratory Bird Mortality Fact Sheet.
  • A recent article in Audubon Magazine suggests “cats were annually knocking off somewhere in the neighborhood of 8 million birds just in rural Wisconsin.” [11] To the magazine’s credit, they used Coleman and Temple’s low estimate (a surprise given the overall tone of the piece). Still, none of the numbers from the Wisconsin Study are scientifically sound (indeed, one can make a strong argument that none of the work constitutes actual research).

For Longcore et al. to cite the Wisconsin Study without even a mention of its numerous flaws, or the rather public admission by one of its authors that their estimates “aren’t actual data,” casts serious doubt on the entire paper. Either they didn’t know how flimsy Coleman and Temple’s work was, or they knew and ignored the facts. Neither approach makes for good science, of course.

*     *     *

Estimating the number of birds killed by cats is difficult enough; demonstrating that their predation is the cause of declining bird populations is an even greater challenge. Nevertheless, Longcore et al. suggest the evidence is both plentiful and compelling. I’ll lay out an argument to the contrary in my next post

References
1. Coleman, J. S., & Temple, S. A. (1996). On the Prowl. Wisconsin Natural Resources, 20, 4–8. http://www.dnr.state.wi.us/wnrmag/html/stories/1996/dec96/cats.htm

2. Coleman, J. S., & Temple, S. A. (1993). Rural Residents’ Free-Ranging Domestic Cats: A Survey. Wildlife Society Bulletin, 21(4), 381–390.

3. Fitzgerald, B. M. (1988). Diet of domestic cats and their impact on prey populations. In D. C. Turner & P. P. G. Bateson (Eds.), The Domestic cat: The biology of its behaviour (1st ed., pp. 123–147). Cambridge; New York: Cambridge University Press.

4. Berkeley, E. P. (2004). TNR Past present and future: A history of the trap-neuter-return movement. Bethesda, MD: Alley Cat Allies.

5. Baker, P. J., Molony, S. E., Stone, E., Cuthill, I. C., & Harris, S. (2008). Cats about town: is predation by free-ranging pet cats Felis catus likely to affect urban bird populations? Ibis, 150, 86-99.

6. Goldstein, L. D., O’Keefe, C. L., & Bickel, H. L. (2003). Addressing “The Wisconsin Study.” http://www.straypetadvocacy.org/html/wisconsin_study.html

7. Clifton, M. (2003). Where cats belong—and where they don’t. Animal People http://www.animalpeoplenews.org/03/6/wherecatsBelong6.03.html

8. Tantillo, J. A. (2006). Killing Cats and Killing Birds: Philosophical issues pertaining to feral cats. In J. R. August (Ed.), Consultations in Feline Internal Medicine Volume 5 (5th ed., pp. 701–708). St. Louis, MO: Elsevier Saunders.

9. Elliott, J. (1994, March 3–16). The Accused. The Sonoma County Independent, pp. 1, 10.

10. American Bird Conservancy (undated). Domestic Cat Predation on Birds and Other Wildlife. The Plains, VA. www.abcbirds.org/abcprograms/policy/cats/materials/predation.pdf

11. Williams, T. (2009). Felines Fatale. Audubon Magazine. http://www.audubonmagazine.org/incite/incite0909.html

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.

References
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.