Posts tagged with Ellen Perry Berkeley

Revisiting “Reassessment”

5 Jan 2011

“Reassessment: A Closer Look at ‘Critical Assessment of Claims Regarding Management of Feral Cats by Trap-Neuter-Return’” has been revised and expanded!

Image of "Reassessment" Document

This paper, a brief review and critique of the essay “Critical Assessment of Claims Regarding Management of Feral Cats by Trap-Neuter-Return” by Travis Longcore, Catherine Rich, and Lauren M. Sullivan, now includes sections on Toxoplasma gondii, the mesopredator release phenomenon, and more. In addition, links and downloadable PDFs have been added to the list of references.

Over the past year, “Critical Assessment” has gotten a great deal of traction among TNR opponents, despite its glaring omissions, blatant misrepresenta­tions, and obvious bias. “Reassessment”—intended to be a resource for a broad audience, including, wildlife and animal control professionals, policymakers, and the general public—shines a bright spotlight on these shortcomings, thereby bringing the key issues back into focus.

Act Locally
Politics is, as they say, local. This is certainly true of the debate surrounding TNR. Policies endorsing TNR, the feeding of feral cats, etc. typically begin with “Town Hall” meetings, or even meetings of neighborhood associations. “Reassessment” provides interested parties with a rigorous, science-based counter-argument to those using “Critical Assessment” as a weapon against feral cats/TNR.

So, once you’ve had a look for yourself, please share generously! Together, we can—in keeping with the mission of Vox Felina—improve the lives of feral cats through a more informed, conscientious discussion of feral cat issues in general, and TNR in particular.

Download PDF

National Feral Cat Day

15 Oct 2010

In honor of National Feral Cat Day, two very appropriate quotes:

A feral animal, having once been domesticated, is not the same as a wild animal. A wild animal may become tamed—indeed, many infant mammals can be tamed—but the ancestors of a feral animal have already been tamed, through the process we know as domestication.—Ellen Perry Berkeley, Maverick Cats: Encounters with Feral Cats

You become responsible, forever, for what you have tamed.
—Antoine de Saint-Exupéry, The Little Prince

Repeat After Me

3 Aug 2010

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.

Learning Your ABC

18 Jun 2010

According to an AP story posted on MSNBC, city officials in Barre, VT, are considering a leash law for cats—effectively prohibiting them from roaming. Such stories tend to vary only in their specifics; quotes from embattled citizens, and feline references that are more dismissive than clever (e.g., in Barre, the debate “sparked a hissing match”) are pretty much a given. And, more often than not, there’s a statement from the American Bird Conservancy (ABC) about the threat free-roaming cats pose to wildlife. This story was no exception:

“Scientists estimate that free-roaming cats kill hundreds of millions of birds, small mammals, reptiles and amphibians each year,” the Virginia-based American Bird Conservancy, which runs a “Cats Indoors!” campaign, says on its website. “Cat predation is an added stress to wildlife populations already struggling to survive habitat loss, pollution, pesticides, and other human impacts.”

Although I don’t know anybody who would argue with ABC’s second point, that first one bears closer inspection.

I discussed a similar claim by ABC’s Senior Policy Advisor, Steve Holmer, in one of my first Vox Felina posts. In January, 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.”

Late last year, an article in Audubon Magazine had published nearly identical figures, citing ABC as its source. [1]

The feral cat estimate comes from a conference paper written by Nico Dauphiné and Robert J. Cooper, available for download via the ABC website. When I pressed Holmer about the authors’ “creative accounting,” he backed off, assuring me that ABC’s materials “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 never received a reply, though, to my inquiries about that “more than one million birds each day” claim. Such incidents are, unfortunately, not uncommon; when it comes to assertions about cat predation and its impact on wildlife, ABC has a rich—and rather shameful—history.

Cats Indoors!
Holmer’s comment to the L.A. Times is just one example of ABC’s concerted effort to use the (largely unquestioning) media in getting their message out. Last year, at a news conference about the “The U.S. State of the Birds” report, ABC’s Darin Schroeder told the press, “education is urgently needed to make the public aware of the toll of pet cats.” Which is precisely what ABC’s Cats Indoors! campaign—launched in 1997—aims to do.

The question is, what kind of education is the public getting from ABC?

  • A 1997 report by ABC claimed, “extensive studies of the feeding habits of domestic, free-roaming cats… show that approximately… 20 to 30 percent [of their diet] are birds.” [cited in 2] In fact, as Ellen Perry Berkeley points out in her book, TNR Past Present and Future: A history of the trap-neuter-return movement, the 20–30% figure was not based on “extensive studies” at all. [2]ABC’s Linda Winter, writing to Berkeley, cited just three sources. Two of them—the now-classic “English village” study by Peter Churcher and John Lawton, and the “Wisconsin Study” by John Coleman and Stanley Temple—have been widely discredited. [3–5] And the third, Mike Fitzgerald’s contribution to “Diet of domestic cats and their impact on prey populations,” [6] was misinterpreted and/or misrepresented by ABC. (As Berkeley notes, Fitzgerald’s data “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!” [2])
  • Winter, director of Cats Indoors! (assuming she’s still at ABC; their website does not list her among the staff), and ABC president George Fenwick were among those thanked “for helpful and constructive reviews” in the Acknowledgements section of Christopher Lepczyk’s 2003 paper, “Landowners and cat predation across rural-to-urban landscapes.” As I detailed in my previous post, Lepczyk’s study is flawed both in terms of its method and analysis, and his predation estimates are highly inflated as a result. The fact that Winter and Fenwick were involved in such as study—at any level—raises questions about ABC’s credibility (and its possible influence on research outcomes).
  • In 2004, Winter misrepresented the results of a survey commissioned by ABC. In “Trap-neuter-release programs: The reality and the impacts,” published in the Journal of the American Veterinary Medical Association, she suggested, “66% of cat owners let their cats outdoors some or all of the time.” [7]In fact, the survey indicated that “35% keep their cats indoors all of the time” and “31% keep them indoors mostly with some outside access.” [9] While Winter’s claim isn’t exactly untrue, it certainly paints a very different picture: rather than one-third, two-thirds of cats are free-roaming. Which, apparently, is exactly how Dauphiné and Cooper read it, combining this with an inflated figure for the number of feral cats to come up with their estimate of “117–157 million free-ranging cats in the United States.” [8] (It’s difficult not to see a certain coziness here: Dauphiné and Cooper citing Winter’s “interpretation” of her own survey results, and Holmer’s reliance on Dauphiné and Cooper’s conference paper.
  • To this day, ABC refers to the highly-criticized Wisconsin Study in its brochure Domestic Cat Predation on Birds and Other Wildlife: “Researchers… estimated that rural free-roaming cats kill at least 7.8 million and perhaps as many as 217 million birds a year in Wisconsin. Suburban and urban cats add to that toll.” [9]And, despite Berkeley’s efforts to untangle their erroneous dietary figures, ABC has backed off only slightly: “In an ongoing, but unpublished, study of cat prey items including stomach contents, scat analysis, observations of kills, and prey remains, birds were 19.6% of 1,976 prey captured by 78 outdoor cats (Temple, S.A, Univ. of WI, personal communication, 1/22/04).”

    [Note: Download Laurie D. Goldstein’s Addressing the Wisconsin Study for a comprehensive critique of this work.]

*     *     *

Don’t get me wrong; I’m all for keeping cats indoors. But what about the feral and stray cats out there—what happens to them? Here, ABC doesn’t seem to have a lot of answers. At least not any they’re willing to be up-front about.

In fact, by disseminating information that is at best misleading—and often, just plain wrong—ABC is doing whatever it can to shape policy in such a way that many of these cats will, one way or another, be killed. Intentional or not, Cats Indoors! has become a kind of Trojan horse for those determined to eliminate all free-roaming cats. Attention can very quickly shift from the impact of a proposed leash law, for example, to the “cat problem” in general.

Although it’s packaged as sound advice for cat owners, the Cats Indoors! campaign has probably had a far greater (deadly) impact on unowned cats than on pet cats.

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

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

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

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

5. Patronek, G.J., “Free-roaming and feral cats—their impact on wildlife and human beings.” Journal of the American Veterinary Medical Association. 1998. 212(2): p. 218–226.

6. 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. p. 123–147.

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

8. 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.

9. 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

A Critical Assessment of “Critical Assessment”—Part 3

10 May 2010

The third 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.

As I’ve suggested previously, much of the “evidence” that Longcore et al. cite regarding cat predation is rather weak. The links between predation and declining wildlife populations (especially birds) are, not surprisingly, no better. According to Longcore et al., “Comparative field studies and population measurements illustrate the adverse effects of feral and free roaming cats on birds and other wildlife.” Let’s take a closer look at some of these studies…

In canyons in San Diego native bird diversity declined significantly with density of domestic cats (Crooks & Soulé 1999). —Longcore et al.

  • Longcore fail to mention the density of people here—the study site was a “moderately sized fragment (~20 ha) [approximately 49 acres] bordered by 100 residences.” [1]
  • It’s also not clear how sites such as this one, which the authors describe as, “undeveloped steep-sided canyons… habitat islands in an urban sea,” correspond to the environment overall. Don’t forget: when Longcore and the Urban Wildlands Group sued the City of Los Angeles last year, it was to put a stop to publicly supported TNR throughout the city.

In a comparative study in Alameda County, California, a site with a colony of feral cats had significantly fewer resident birds, fewer migrant birds, and fewer breeding birds than a control site without cats (Hawkins 1998). Ground-foraging species, notably California Quail (Calipepla californica) and California Thrashers (Toxostoma redivivum), were present at the control site but never observed at the site with cats. Native rodent density was drastically reduced at the site with cats, whereas exotic house mice (Mus musculus) were more common (Hawkins 1998). —Longcore et al.

Hawkins’ dissertation [2] is so problematic—and cited frequently enough as “evidence” of the impact of cats on wildlife—that it warrants a post of its own. Here, I’ll touch on just a few issues.

  • Hawkins describes the “cat” and “no-cat” sites as being similar enough that a valid A-B comparison is appropriate. But a closer look at the study suggests otherwise. Much of the cat site bordered the park’s lake and marina, not far from a number of picnic sites. Hawkins notes that there were more people in the cat area, but doesn’t even admit to the possibility that their presence may have influenced the numbers of birds and rodents he observed there.
  • In addition, the presence of pesticides may have played a role. According to a 2002 report (the earliest I was able to find) from the East Bay Regional Park District, “The focus of Lake Chabot’s weed control efforts are vegetation reduction within the two-acre overflow parking lot, picnic sites and firebreaks around park buildings, corp. yard, service yard, and the Lake Chabot classroom.” [3] Now, Hawkins’ fieldwork was done in 1995 and 1996, but if there was any pesticide use going on during the study period, it may have affected the results—especially if the pesticide was distributed differently across the two sites.
  • Hawkins writes, “The preference of ground feeding birds for the no-cat treatment was striking; for example, California quail were seen almost daily in the no-cat area, whereas they were never seen in the cat area.” What’s more striking to me, though, is the fact that five of the nine ground-feeding species included in the study showed no preference for the cat or no-cat area—a point Hawkins downplays, and Longcore et al. ignore entirely.
  • Finally, it’s not clear how this study constitutes an experiment at all. Hawkins chose two sites, one where cats were being fed, and another (approximately two miles away) where cats were not being fed. We have no idea what the cat area was actually like prior to the cats being fed there—Hawkins merely assumes the populations of birds and rodents would have been identical to those found at the no-cat site. We also have no idea what effect the feeding had—what if the cats were present but had to fend for themselves? And we don’t know if the cats were sterilized, or what impact that might have had on the study. In other words, Hawkins doesn’t actually know enough about what’s going on at the two sites to conclude, as he does, that “it is not prudent to manage for wildlife and allow cat feeding in the same parks.”

In Bristol, United Kingdom Baker et al. (2005) calculated that the predation rates by cats on 3 bird species in an urban area is high relative to annual productivity, which led the authors to suggest that the area under study may be a habitat sink. —Longcore et al.

  • Also, Longcore et al. fail to mention that Baker et al. concede an important point: “collectively, despite [cats] occurring at very high densities, the summed effects on prey populations appeared unlikely to affect population size for the majority of prey species.”
  • In addition, a subsequent study (also conducted in Bristol) involving two of the authors, suggests that much of the predation observed was compensatory rather than additive. That is, many of these birds would have, for one reason or another, died anyhow, whether the cats were present or not. Specifically, the authors found that “birds killed by cats in this study had significantly lower fat and pectoral muscle mass scores than those killed by collisions.” [6] Baker at al. are cautious about these findings, suggesting, “the distinction between compensatory and additive mortality does… become increasingly redundant as the number of birds killed in a given area increases: where large numbers of prey are killed, predators would probably be killing a combination of individuals with poor and good long-term survival chances.” But once again, their estimates of birds killed by cats are inflated by a factor of 3.3, as described above—thereby raising doubts about any level of “redundancy.”
  • Another study to investigate compensatory vs. additive predation was more conclusive. Møller and Erritzøe compared the average spleen mass of birds killed by cats to that of birds killed in collisions with windows found that, “small passerine birds falling prey to cats had spleens that were significantly smaller than those of conspecifics that died for other reasons,” concluding that the birds killed by cats “often have a poor health status.” [7] In other words, the birds killed by cats were among the population least likely to survive anyhow.

Clearly, this is a complex—not to mention contentious—issue. But Longcore et al. make it out to be remarkably straightforward. The “adverse effects of feral and free roaming cats on birds and other wildlife,” they seem to suggest, are widely accepted common knowledge.

*     *     *

Then, too, there are those—and there are many—who have disputed the broad-brush claims about the impact of cat predation on wildlife. Consider, for example, the following studies:

  • Biologist C.J. Mead, reviewing the deaths of “ringed” (banded) birds reported by the public, suggests that cats may be responsible for 6.2–31.3% of bird deaths. “Overall,” writes Mead, “it is clear that cat predation is a significant cause of death for most of the species examined.” But the relationship between bird deaths and population declines is complex. In fact, Mead concludes that “there is no clear evidence of cats threatening to harm the overall population level of any particular species… Indeed, cats have been kept as pets for many years and hundreds of generations of birds breeding in suburban and rural areas have had to contend with their predatory intentions.” [8]
  • Mike Fitzgerald and Dennis Turner come to essentially the same conclusion. (Their contribution to The Domestic Cat: The Biology of its Behaviour is a must-read for anybody interested in the subject.) “We consider that we do not have enough information yet to attempt to estimate on average how many birds a cat kills each year,” write Fitzgerald and Turner. “And there are few, if any studies apart from island ones that actually demonstrate that cats have reduced bird populations.” [9]
  • Martin, Twigg, and Robinson conclude more broadly, “it is not possible to make any inferences concerning the real impact of feral cats on prey populations from dietary studies.” [10]

Given the scope of their essay, perhaps it’s understandable that Longcore et al. were unable to cover each aspect of this rather broad topic in a comprehensive manner. Nevertheless, the amount of research into cat predation and declining bird populations—a critical piece of the puzzle, to be sure—that was omitted, glossed over, and/or misrepresented suggests a clear agenda. Read carefully, their essay comes across as not as scientific discourse, but as fodder for a marketing campaign. (And, given the number of wildlife conservation/bird advocacy groups that have posted it on their websites—not to mention the L.A. Superior court decision—it’s been effective.)

*     *     *

Many proponents of TNR will acknowledge that the practice is not appropriate for all environments. Crooks and Soulé’s work in San Diego’s canyon country (cited previously), writes Ellen Perry Berkeley, “suggests to even the most ardent TNR advocate that such a landscape might not be the best place for TNR… The world is a complicated place.” [11] Gary J. Patronek, the former Director of the Center for Animals and Public Policy at the Cummings School of Veterinary Medicine at Tufts University, and one of the founders of the Hoarding of Animals Research Consortium, goes further: “the release of cats into an environment where they would impact endangered or threatened species, or even into wildlife preserves or refuges, is inexcusable.” [12]

This, I worry, is a slippery slope. Given the current nature of the cat debate, how long would it be before every alley, Dumpster, and abandoned property is deemed a wildlife preserve? And, given the number of endangered and threatened species—and their wide range—would there be any environment left for cats? Nevertheless, Patronek’s larger point is an important one:

I do not believe that this is being advocated by cat protectors who see urban, managed colonies as an imperfect but still preferable alternative to the euthanasia of healthy animals. Abandoned pet cats whose own habitat has been reduced to colonies, and the wild species endangered by clear-cutting or beachfront development, are casualties of the same callous disregard for the lives of animals. I see little justification for shifting the role of cats to that of scapegoat.

For Longcore and the Urban Wildlands Group (and others, too, of course), though, there’s simply no place for TNR anywhere. But there’s something even more troubling with their argument: they’re asking the wrong questions. As Patronek puts it so eloquently:

If the real objection to managed colonies is that it is unethical to put cats in a situation where they could potentially kill any wild creature, then the ethical issue should be debated on its own merits without burdening the discussion with highly speculative numerical estimates for either wildlife mortality or cat predation. Whittling down guesses or extrapolations from limited observations by a factor of 10 or even 100 does not make these estimates any more credible, and the fact that they are the best available data is not sufficient to justify their use when the consequence may be extermination for cats… What I find inconsistent in an otherwise scientific debate about biodiversity is how indictment of cats has been pursued almost in spite of the evidence, and without regard to the differential effects of cats in carefully selected, managed colonies, versus that of free-roaming pets, owned farm cats, or truly feral animals. Assessment of well-being for any is an imprecise and contentious process at best. Additional research is clearly needed concerning the welfare of these cats.

In a future post, I’ll get into the ways Longcore et al. would have us measure the success of TNR.

References
1. Crooks, K.R. and Soule, M.E., “Mesopredator release and avifaunal extinctions in a fragmented system.” Nature. 1999. 400(6744): p. 563.

2. Hawkins, C.C., Impact of a subsidized exotic predator on native biota: Effect of house cats (Felis catus) on California birds and rodents. 1998, Texas A&M University.

3. Brownfield, N.T., 2002 Annual Analysis of Pesticide Use East Bay Regional Park District. 2003, East Bay Regional Park District.

4. Baker, P.J., et al., “Impact of predation by domestic cats Felis catus in an urban area.” Mammal Review. 2005. 35(3/4): p. 302-312.

5. Kays, R.W. and DeWan, A.A., “Ecological impact of inside/outside house cats around a suburban nature preserve.” Animal Conservation. 2004. 7(3): p. 273-283.

6. Baker, P.J., et al., “Cats about town: is predation by free-ranging pet cats Felis catus likely to affect urban bird populations?“ Ibis. 2008. 150: p. 86-99.

7. Møller, A.P. and Erritzøe, J., “Predation against birds with low immunocompetence.” Oecologia. 2000. 122(4): p. 500-504.

8. Mead, C.J., “Ringed birds killed by cats.” Mammal Review. 1982. 12(4): p. 183-186.

9. Fitzgerald, B.M. and Turner, D.C., Hunting Behaviour 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. 2000, Cambridge University Press. p. 151–175.

10. Martin, G.R., Twigg, L.E., and Robinson, D.J., “Comparison of the Diet of Feral Cats From Rural and Pastoral Western Australia.” Wildlife Research. 1996. 23(4): p. 475-484.

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

12. Patronek, G.J., “Letter to Editor.” Journal of the American Veterinary Medical Association. 1996. 209(10): p. 1686–1687.

A Critical Assessment of “Critical Assessment”—Part 2

5 May 2010

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