Appealing to Our Better Nature

It’s not every day that I hear from somebody whose work I’ve criticized. (In fact, I rarely receive a response from those I reach out to for comments or clarification.) Imagine my surprise, then, when I received an e-mail from somebody involved with Nature Canada’s “cats indoors” campaign who was interested in better understanding my objections. Even more surprising was my subsequent telephone conversation with Sarah Cooper: exactly the sort of thoughtful, open exchange I’d hoped for when I launched Vox Felina six years ago today.

It doesn’t hurt that Cooper, who’s largely responsible for Nature Canada’s communication strategy for the campaign, is curious, witty, and charming.

Over the course of our conversation (nearly two hours, if I recall correctly), she gave me plenty to think about. So, to mark Vox Felina’s six-year anniversary, I want to reflect on that previous post a little bit and ask readers to weigh in as well. Read more

“Cats Indoors” Campaigns: A Grave Threat to Outdoor Cats?

In the interest of full disclosure: I keep my cats indoors 24 hours a day, seven days a week. It’s an uncompromising policy I’ve adopted for their safety — and my sanity. I encourage others to keep their cats indoors, too. Why, then, do I object so strenuously to “cats indoors” efforts, such as Nature Canada’s recently launched Keep Cats Safe and Save Bird Lives campaign?

It’s a question to which I’ve given a great deal of thought since I first began blogging about the ongoing witch-hunt against outdoor cats nearly six years ago, and it mostly comes down to the following: Read more

The (Ig)Noble Pursuit of Public (Dis)Service

Two new public service campaigns from the American Bird Conservancy fly in the face of science, public opinion, and common sense.

For nearly 20 years now, it seems the people at the American Bird Conservancy have been willing to say whatever they thought they could get away with to promote the lethal roundup of “feral” cats. Unburdened by the constraints of integrity, PR ought to be easy for ABC. Two recent public service announcements, however, suggest otherwise.

Indeed, ABC’s latest salvo in their war on cats suggests that the organization’s grasp of effective messaging is no better than their grasp of science. (And this, as every regular reader will understand immediately, is saying something.) Read more

Exceptional Predator

Photo of cat leaping after birdUsing Google to translate the page’s contents, it seems this bird—despite “mock[ing] the cat and with loud cries of diving at him from the branches of acacia”—was yet another one that got away.

In the third edition of his massive book Ornithology—“the classic text for the undergraduate ornithology course,” according to the description on Amazon.com—Frank Gill writes:

“Natural predators are a major source of annual mortality among birds, especially nestlings, incubating females, and young birds in their first year. Relentless predation is a driving force of natural selection for escape behaviors, camouflage plumage, and social behavior. With some conspicuous exceptions, however, predators don’t limit or regulate the bird populations on which they prey [1]. Instead, they take weak, sick, and young birds, many of which are part of the surplus that exceeds locally limiting food supplies.” [2, p 545]

For Gill, it seems, it’s all very straightforward; this, after all, is how Nature works. (It should be noted that, just one paragraph later, the author makes a clear distinction between islands and other habitats: “The endangerment and extinction of island birds by introduced predators is a conspicuous exception to the statement that predators don’t limit bird populations.”)

Unequal Treatment Under the (Natural) Law
Nobody opposed to TNR would deny that cats are predators—so why won’t they admit that the birds and other wildlife killed by cats are generally among, as Gill puts it, the “weak, sick, and young”?

The Carolina Raptor Center, for example, describes the role of predatory birds targeting bird feeders this way:

“Songbirds are part of the food chain just like other animals and their predators are going to look for the easiest targets. The birds that hawks are usually able to catch at feeders are the slow and sick ones. The strong and healthy ones escape, allowing their survival to produce more healthy babies.”

Cats, however, are a different matter altogether. According to the Carolina Raptor Center, they “kill a lot more birds then hawks do because hawks only kill for food, where cats kill for the sport of it.” I’ve never seen any scientific evidence to support such a claim, which may explain why so many have instead argued—again, without any support—that cats compete with raptors for food.

Who’s Crazed Now?
It wasn’t Gill’s book that got me thinking about this, though, but a comment posted last month on the Bountiful Films blog, following the release of their documentary Cat Crazed.

After listening to a CBC interview with director Maureen Palmer, whose “science” was clearly coming straight from the American Bird Conservancy, I posted a comment, stating in part:

“What you won’t find [from organizations opposing TNR] is any mention of the studies that show rather convincingly that birds killed by cats tend to be unhealthy compared to those killed by building collisions, say. Even high predation rates do not equate to population declines—as many scientists have noted.”

I also included a link to my “Predatory Blending” post. Which promptly drew fire from somebody calling him/herself “Catbird”:

“Where cats cause documented extinctions and extirpations, cat predation is additive (e.g., Hawkins 1998, Crooks and Soule 1999, Nogales et al. 2004). Researchers are interested in knowing if some cat predation is compensatory (that is, killing animals that would die anyway) (Beckerman et al. 2007, Baker et al. 2008, van Heezik et al. 2010). The purported evidence of compensatory predation is a study showing that cat-killed birds have larger spleens (indicating that they are less healthy) than birds killed by other sources (e.g., windows) (Moller and Erritzoe 2000). Other researchers found that birds killed by cats had less fat reserves and lower muscle mass than those killed in collisions (Baker et al. 2008), but warned against assuming that this corresponded with lower fitness of these individuals. In neither instance is it possible to conclude that individuals killed by cats would have died otherwise.”

Actually, Møller & Erritzoe don’t suggest that the birds captured by cats “would have died otherwise.” But, they are quite clear about the implications of their research:

“The present study has suggested that predators like the domestic cat may select against individuals with a weak immune system, leaving a disproportionate fraction of immunocompetent individuals as survivors.” [3]

What Møller & Erritzoe observed is very much in line with what Gill describes as typical predatory behavior.

Still, though, I’m not necessarily surprised with Catbird’s “interpretation” of the science, given his/her comments and tone elsewhere in the discussion. What’s far more troubling is that so few studies on the predatory habits of cats address the topic in any meaningful way.

Sins of Omission
Take that 2008 study by Baker et al., for example. The authors are, just as Catbird suggests, quite cautious about their findings:

“The distinction between compensatory and additive mortality does, however, 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. The predation rates estimated in this study would suggest that this was likely to have been the case for some species on some sites.” [4]

But, as I’ve pointed out previously, the authors’ predation rates are inflated—in part due to their unquestioning application of the dubious multiplier proposed by Kays and DeWan. [5] Baker et al. also use low estimates of breeding density—all of which combines to diminish the apparent level of compensatory predation. Were these estimates adjusted to better reflect the conditions at the site, the “redundancy” the authors refer to would be reduced considerably.

(Frankly, Baker and his colleagues seemed quite eager to demonstrate that Bristol’s cats were negatively affecting bird populations; in an earlier study, they suggested—based, I would argue, on insufficient information—that the area might be a “dispersal sink for more productive neighboring areas.” [6])

On the other hand, at least Baker et al. acknowledge Møller and Erritzoe’s work. Many other studies don’t even go that far.

Coleman and Temple, [7] for example, failed to consider the role of compensatory predation—despite the fact that they cite sources/studies that do. [8–10] And Temple himself addresses this very topic in his 1987 paper Do Predators Always Capture Substandard Individuals Disproportionately From Prey Populations?

Using a trained Red-tailed hawk to prey on eastern chipmunks, cottontail rabbits, and gray squirrels, Temple developed the “proposition that substandard individuals are captured disproportionately when the type of prey is relatively difficult to capture but not when it is relatively easy to capture.” [11]

Which seems a very fitting description for the general case of a cat attempting to capture an adult bird. (Ground-nesting and ground-feeding birds would likely be easier prey, though Hawkins’ PhD dissertation work [12] suggests that even this assumption deserves careful scrutiny.)

Longcore et al. never mention Møller and Erritzoe (one of many shortcomings I address in “Reassessment”); neither do Dauphine and Cooper. [13]

And ABC doesn’t go near the topic of compensatory predation. (Ironic since, unlike cats, most of the “threats to birds” listed by ABC (e.g., pesticides, pollution, oil spills, collisions with towers, buildings, wind turbines, and power lines, etc.) are clearly nondiscriminatory in terms of bird mortality.)

•     •     •

Is it any wonder that a reasonable discussion about the impacts of free-roaming cats on wildlife is so elusive? The same stakeholders that condemn these cats for their predatory nature too often refuse to acknowledge the nature of predation itself.

Literature Cited
1. Newton, I., Population limitation in birds. 1998, San Diego: Academic.

2. Gill, F.B., Ornithology. 3rd ed. 2007, New York: W.H. Freeman.

3.  Møller, A.P. and Erritzøe, J., “Predation against birds with low immunocompetence.” Oecologia. 2000. 122(4): p. 500–504. http://www.springerlink.com/content/ghnny9mcv016ljd8/

4. 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. http://www.ingentaconnect.com/content/bsc/ibi/2008/00000150/A00101s1/art00008

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. http://dx.doi.org/10.1017/S1367943004001489

www.nysm.nysed.gov/staffpubs/docs/15128.pdf

6. 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. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2907.2005.00071.x/abstract

7. Coleman, J.S. and Temple, S.A., How Many Birds Do Cats Kill?, in Wildlife Control Technology. 1995. p. 44. http://www.wctech.com/WCT/index99.htm

8. 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.

9. Churcher, P.B. and Lawton, J.H., “Predation by domestic cats in an English village.” Journal of Zoology. 1987. 212(3): p. 439-455. http://dx.doi.org/10.1111/j.1469-7998.1987.tb02915.x

10. Errington, P.L., “Notes on Food Habits of Southwestern Wisconsin House Cats.” Journal of Mammalogy. 1936. 17(1): p. 64–65. http://www.jstor.org/stable/1374554

11. Temple, S.A., “Do Predators Always Capture Substandard Individuals Disproportionately From Prey Populations? Ecology. 1987. 68(3): p. 669–674. http://www.esajournals.org/doi/abs/10.2307/1938472

12. 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

13. Dauphine, 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. http://www.pwrc.usgs.gov/pif/pubs/McAllenProc/articles/PIF09_Anthropogenic%20Impacts/Dauphine_1_PIF09.pdf

Inside Job

Results from the American Pet Products Association’s 2009­­–2010 National Pet Owners Survey suggest that cats in this country are spending more time indoors than ever before. Although the proportion of owners keeping their cats inside at night has remained relatively steady since 1998 (at approximately 66%), their has been a 14% increase in daytime confinement (from 56% to 64%) over the same period. [1]

Indoor&Outdoor Access-APPA

It must be noted that owners were asked where they usually kept their cat(s), thereby raising some doubts about the accuracy of their responses. (There are actually two issues here: first is the level of truthfulness—did owners, intentionally or not, provide accurate information? But there is also the obvious ambiguity surrounding the term usually.) Nevertheless, these results correspond reasonably well with those of two earlier surveys: one commissioned by the American Bird Conservancy (ABC) in 1997, [2] the other conducted by Clancy et al. in 2001 [3] (the only other surveys I’ve found that investigated this issue specifically).

The ABC’s study (in which 250 cat owners participated in a telephone survey) indicated that “35% keep their cats indoors all of the time,” while “31% keep them indoors mostly with some outside access.” [2]

The 2001 survey included 168 cat owners, each of whom was part of the Feline Health Study, conducted at the Foster Hospital for Small Animals, Cummings School of Veterinary Medicine, Tufts University. Sixty percent of these cats were “strictly indoor cats,” while 40% “had some level of outdoor access.” [3] Probing further, Clancy et al. discovered that nearly half of the cats with outdoor access were outside for two or fewer hours a day. And 29% of them were outdoors for less than an hour each day. [3]

Considering the differences in sampling (most notably the fact that participants in the 2001 survey were all clients of a veterinary hospital, whereas APPA survey results for 2000 indicate that 27% of cat owners did not visit the vet in the previous 12 months), and the inherent uncertainty surrounding the terms mostly, usually, and some, the results of these three surveys are remarkably similar.

Counting Cats
Such findings are critical for developing accurate estimates of the number of birds killed by cats (assuming a reasonable level of accuracy is achievable, given the complexity of the issue). Simply put, cats that don’t go outside can’t kill birds.

Recognizing this, some researchers have inflated their figures for cats allowed outdoors. [4–6]

Dauphiné and Cooper, [6] for instance, cite the APPA’s 2007–2008 survey when referring to the number of owned cats in the U.S., but either ignored or overlooked its findings about confinement: 63% of owners reported that they kept their cat(s) indoors during the day, 70% during the night. (It’s also possible that the authors consulted only the APPA’s online summary, which probably didn’t include this information.)

By contrast, Dauphiné and Cooper claim that 65% of pet cats “are free-ranging outdoor cats for at least some portion of the day,” [6] citing not the APPA survey, but Linda Winter’s 2004 paper, “Trap-neuter-release programs: the reality and the impacts” (which can be downloaded here). Indeed, Winter, the former director of the ABC’s Cats Indoors! campaign, had suggested as much—misrepresenting the findings of a study commissioned by her own organization:

“A 1997 nationwide random telephone survey indicated that 66% of cat owners let their cats outdoors some or all of the time.” [7]

Double the proportion of cats allowed outdoors, and—just like that—the number of birds killed by pet cats doubles too. (Dauphiné and Cooper actually go much further, employing some grossly inflated predation rates as well.)

Counting Birds
Of course, such estimates do not necessarily relate directly to population impacts. The predation may be largely compensatory, for example; and there are source-sink dynamics to be considered as well.

Nevertheless, researchers persist—more often, it seems, in pursuit of staggering, media-friendly figures than a better understanding of what’s actually going on (e.g., Dauphiné and Cooper’s bumper-sticker-worthy “one billion birds”). As a result, the scientific literature is plagued with some rather spectacular failures where predation numbers are concerned (e.g., The Wisconsin Study, Christopher Lepczyk’s dissertation, Carol Fiore’s thesis, etc.).

*     *     *

The surprising level of agreement among the three “outdoor access” studies provides researchers a rare opportunity to agree among themselves. Which, in turn, could move us closer to an honest debate of the larger issues—arguing about which action is most appropriate, for instance, rather than about whose numbers are most valid.

Despite how results of these surveys have been—as recently as last year—overlooked, ignored, and misrepresented, I remain cautiously optimistic. As Patronek has suggested, “predation of songbirds tends to be noticed because it takes place during the day.” [8] It’s time predation research received the same kind of visibility. Sunlight, after all, is said to be the best of disinfectants.

Note: There is a an amendment to this post here.

Literature Cited
1. APPA, 2009–2010 APPA National Pet Owners Survey. 2009, American Pet Products Association: Greenwich, CT.

2. ABC, Human Attitudes and Behavior Regarding Cats. 1997, American Bird Conservancy: Washington, DC. http://www.abcbirds.org/abcprograms/policy/cats/materials/attitudes.pdf

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

4. 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

5. Lepczyk, C.A., Mertig, A.G., and Liu, J., “Landowners and cat predation across rural-to-urban landscapes.” Biological Conservation. 2003. 115(2): p. 191-201.

6. 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.

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. 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.

Learning Your ABC

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

The Work Speaks—Part 6: Pain by Numbers

In April, Conservation Biology published a comment authored by Christopher A. Lepczyk, Nico Dauphiné, David M. Bird, Sheila Conant, Robert J. Cooper, David C. Duffy, Pamela Jo Hatley, Peter P. Marra, Elizabeth Stone, and Stanley A. Temple. In it, the authors “applaud the recent essay by Longcore et al. (2009) in raising the awareness about trap-neuter-return (TNR) to the conservation community,” [1] and puzzle at the lack of TNR opposition among the larger scientific community:

“…it may be that conservation biologists and wildlife ecologists believe the issue of feral cats has already been studied enough and that the work speaks for itself, suggesting that no further research is needed.”

In fact, “the work”—taken as a whole—is neither as rigorous nor as conclusive as Lepczyk et al. suggest. And far too much of it is plagued by exaggeration, misrepresentations, errors, and obvious bias. In Part 5 of this series, I critiqued Cole Hawkins’ 1998 PhD dissertation. Here, I’m going to untangle some of Lepczyk’s own PhD work: Landowners and cat predation across rural-to-urban landscapes, published in 2003.

The Study
In this study, surveys were distributed across three southeastern Michigan landscapes (rural, suburban, and urban) corresponding to established breeding bird survey (BBS) routes. [2] Among the survey questions:

“If you or members of your household own cats that are allowed access to the outside, approximately how many dead or injured birds a week do all the cats bring in during the spring and summer months (April through August) (0, 1, 2–3, 4–5, 6–7, 8–9, 10–15, 16–20, more than 20)?”

Based on 968 surveys returned from 1654 private landowners (a decent response rate of 58.5%), Lepczyk et al. conclude:

“Across the three landscapes there were ~800 to ~3100 cats, which kill between ~16,000 and ~47,000 birds during the breeding season, resulting in a minimum of ~1 bird killed/km/day.”

Increasing Uncertainty
How do Lepczyk and his collaborators arrive at these figures? It’s not entirely clear, actually. Despite numerous attempts, I’ve been unable to follow all of their calculations. However, using their data, I developed my own estimate: 1,119 outdoor cats, 511 of which were reported to be successful hunters.

Using this figure, I then summed across all three landscapes the birds killed or injured, plus those killed or injured by non-respondents’ hunting cats (based on the ratio of hunters to outdoor cats owned by respondents, or about 50%). The resulting estimate is 15,856 birds killed over the 22-week breeding season—close to the low estimate suggested by Lepczyk et al., but just a third of their maximum.

So, why the discrepancy?

One reason is that, at least for some of their estimates, Lepczyk et al. assumed that every landowner who didn’t respond to the survey owned outdoor cats. This, despite their survey results, which indicated that only about one-third of landowners fell into this category.

But the authors go further, generating predation estimates based on pure speculation, specifically that “non-respondents have 150% the number of outdoor cats as respondents.” [2] It should be noted that Lepczyk et al. also ran another scenario in which non-respondents had half the outdoor cats as did respondents—but, again, in both cases they assume that every non-respondent owned outdoor cats.

As a result of this approach, the authors end up in some strange territory: the estimated number of cats owned by non-respondents (based on the assumptions described above) far exceeds the number owned by respondents—by more than a two-to-one margin, in some cases. If the greatest impacts are going to be attributable to non-respondents, then what’s the point of doing the survey in the first place? There are accepted methods by which one can manage uncertainty—statistical analysis, confidence intervals, and the like. What Lepczyk et al. have done serves just one purpose: to inflate apparent predation rates.

Skewed Distributions
In addition to the flaws described above, there are some fundamental errors in the way the authors handle their data. Like so many others, Lepczyk et al. ignore the fact that their data is not normally distributed:

  1. Lepczyk et al. use the average number of birds killed/cat to calculate the total number of bids killed for each of the three landscapes. As I discussed previously), this is a highly positively skewed distribution—using a simple average, therefore, greatly overestimates the cats’ impact (by as much as a factor of two).
  2. A similar error is made when the authors use an average to describe the number of outdoor cats owned by each landowner. Again, because this is a skewed distribution, their use of a simple average exaggerates the extent of predation.
  3. The two inflated figures described in (1) and (2) are multiplied together, further inflating estimated predation rates.

Barratt has suggested that “median numbers of prey estimated or observed to be caught per year are approximately half the mean values, and are a better representation of the average predation by house cats based on these data.” [3] Accounting for the first point alone, then, my estimate is reduced to 8,000 birds killed over the 22-week breeding season.

Accounting for the second point is somewhat trickier. For one thing, we don’t know what constitutes an outdoor cat here—the survey simply asked respondents if they owned cats “that are allowed access to the outdoors.” [2] However, we do know the results of a 2003 survey, which indicated 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. [4] Although these figures almost certainly reflect owners in urban and suburban landscapes more than those in rural landscapes, it’s clear that a simple yes-or-no question on the subject is insufficient. Indeed, such a question will invariably overestimate the number of “outdoor cats”—which in turn overestimates predation rates.

This, coupled with the error inherent in using a simple average, pushes predation estimates lower. And the third point reduces those estimates further still. Taken together, these corrections could put my estimate closer to 4,000 birds. More important, the upper estimate proposed by Lepczyk et al.—47,000 birds—could easily be 10 times too high.

The Small Print
Despite their inflated figures, Lepczyk et al. suggest—rather absurdly, in light of the substantial flaws described above—that perhaps their estimates are actually too conservative:

“One caveat to our study is that landowners may have underestimated the number of cats they allow access to the outside. Such a result was found in a similar study of landowners in Wisconsin (Coleman and Temple, 1993).” [1] (Note: After reviewing “Rural Residents’ Free-Ranging Domestic Cats: A Survey,” [5] I’ve found no evidence of such a result.)

“… we found that a very common volunteered response among landowners that had no outdoor cats was that either their neighbors owned outdoor cats or that feral cats were present in the vicinity of their land… [suggesting] that at least some landowners under reported or chose not to report the number of outdoor cats they owned.”

But what about their reports of birds brought home killed or injured—how trustworthy were those? After all, the survey (mailed during the first week of October) asked respondents to recall the number of birds their cat(s) brought home April through August. Surely, there was a lot of guesswork involved. In fact, David Barratt found this kind of guesswork to overestimate predation rates. In a study published five years prior to “Landowners and Cat Predation,” Barratt concluded, “predicted rates of predation greater than about ten prey per year generally over-estimated predation observed.” [3]

The two studies cannot be compared directly for a number of reasons, but by way of comparison, the average predation rate used by Lepczyk et al. is approximately 31 birds/cat for the 22-week breeding season. Using Barratt’s work, in which the “heaviest” six continuous months correspond to about 58% of yearly prey totals, [6] I converted this to a yearly rate of 53 birds/cat/year. Barratt has shown that the actual predation rate, at this level, is less than half the rate predicted by cat owners. In other words, predictions of 50 birds/year generally correspond to catches closer to 25 birds/year.

While Lepczyk et al. emphasize the potential for under-estimating predation levels, they never consider the risk of over-estimating these levels—or their most obvious potential source of error: landowners’ recollections of birds killed. The authors question respondents’ reports of outdoor cats, but accept without question their reports of birds injured or killed over the previous six-month period. And, as Barratt indicated, such reports can be inflated by a factor of two or more!

Something else I find troubling comes, of all places, from the Acknowledgements section. Among those thanked “for helpful and constructive reviews” are American Bird Conservancy (ABC) president George Fenwick and Linda Winter, director of ABC’s Cats Indoors! campaign. It’s not clear how Fenwick and Winter contributed to the final paper, but their involvement on any level raises questions about possible bias. Certainly, Winter has credibility issues when it comes to “research” about the impact of free-roaming cats on birds, as I’ve already described (see also pp. 18–24 of TNR Past present and future: A history of the trap-neuter-return movement [7]).

*     *     *

The same year Lepczyk’s paper was published, the American Veterinary Medicine Association held an Animal Welfare Forum “devoted to the management of abandoned and feral cats.” [8] In attendance were more than 200 veterinarians, animal control officials, wildlife conservationists, and animal advocates—each with a different perspective on feral cats in general and TNR in particular.

In welcoming this diverse group, then-President-Elect Bonnie Beaver recognized the range of contentious issues before them:

“Feral cats evoke hot debates about ecological issues, individual cat welfare, human responsibilities, intercat disease transmission, humaneness, zoonosis control, and management and dissolution of unowned cats.” [8]

Amidst the “hot debate,” though, Beaver was optimistic:

“We will not always agree, but we will come away with increased knowledge and a renewed commitment to work for the welfare of all the animals with which we share the earth” [8]

While I tend to share Beaver’s optimism, I think the debate is hurt—if not derailed entirely—by the publication of research aimed not at increasing our collective knowledge, but rather at supporting a particular position. Like Cole Hawkins’ dissertation, “Landowners and Cat Predation” is, at best, an interesting pilot study for subsequent work. And yet, it’s widely—and uncritically—cited in the feral cat/TNR literature. Longcore et al., for example, refer to it as “evidence [indicating] that cats can play an important role in fluctuations of bird populations,” [9] despite the fact that Lepczyk et al. don’t actually address the issue of bird populations at all. More recently, Dauphiné and Cooper use the inflated predation rate suggested by Lepczyk et al. (along with rates proposed by other researchers) to arrive at their “billion birds” figure. [10]

The method employed in “Landowners and Cat Predation”—asking owners of cats to recall the number and species of birds over the previous six-month period—invites overestimation from the very outset. Lepczyk et al. then inflate these numbers through both careless (e.g., using averages to describe skewed data) and deliberate (e.g., assuming all non-respondents owned cats—perhaps 50% more than respondents did) means. Rather than getting us any closer to the truth about cat predation, this study only obscured it further.

Worse, it’s been packaged and sold—and subsequently “bought”—as rigorous science, thereby giving it an undeserved legitimacy. Such efforts are impediments to knowledge and understanding—and therefore, to progress.

References
1. Lepczyk, C.A., et al., “What Conservation Biologists Can Do to Counter Trap-Neuter-Return: Response to Longcore et al.” Conservation Biology. 2010. 24(2): p. 627-629.

2. Lepczyk, C.A., Mertig, A.G., and Liu, J., “Landowners and cat predation across rural-to-urban landscapes.” Biological Conservation. 2003. 115(2): p. 191-201.

3. Barratt, D.G., “Predation by house cats, Felis catus (L.), in Canberra, Australia. II. Factors affecting the amount of prey caught and estimates of the impact on wildlife.” Wildlife Research. 1998. 25(5): p. 475–487.

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

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

6. Barratt, D.G., “Predation by House Cats, Felis catus (L.), in Canberra, Australia. I. Prey Composition and Preference.” Wildlife Research. 1997. 24(3): p. 263–277.

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

8. Kuehn, B.M. and Kahler, S.C. The Cat Debate. JAVMA Online 2004 November 27, 2009 [accessed 2009 December 24].  http://www.avma.org/onlnews/javma/jan04/040115a.asp.

9. 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.

10. 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.

The Work Speaks—Part 1: Lost in Translation

In April, Conservation Biology published a comment authored by Christopher A. Lepczyk, Nico Dauphiné, David M. Bird, Sheila Conant, Robert J. Cooper, David C. Duffy, Pamela Jo Hatley, Peter P. Marra, Elizabeth Stone, and Stanley A. Temple. In it, the authors “applaud the recent essay by Longcore et al. (2009) in raising the awareness about trap-neuter-return (TNR) to the conservation community,” [1] and puzzle at the lack of TNR opposition among the larger scientific community:

“…it may be that conservation biologists and wildlife ecologists believe the issue of feral cats has already been studied enough and that the work speaks for itself, suggesting that no further research is needed.”

In fact, “the work”—taken as a whole—is neither as rigorous nor as conclusive as Lepczyk et al. suggest. And far too much of it is plagued by exaggerations, misrepresentations, errors, and obvious bias. For the next few posts, I’m going to present a sampling of its more serious flaws, beginning with how some researchers “reinterpret” work of others to suit their own purposes.

Tell It Like It Is
Studies of cat predation frequently cite the work of William G. George, who, in 1974, published a paper documenting his meticulous observations of the hunting behavior of three cats on his southern Illinois farm. “The results,” wrote George, “established a basis for examining the possibility that cat predation may result in depleted winter populations of microtine rodents and other prey of Red-tailed Hawks, Marsh Hawks, and American Kestrels.” [2]

Thirty years later, David A. Jessup interpreted things rather differently, giving George’s work an additional—and unwarranted—degree of certainty. Gone are the doubts that George expressed—first, regarding the impact of cat predation on rodent and other prey populations; second, regarding the relationship between these populations and the raptors that feed on them. For Jessup—who offers no additional evidence—it’s all very straightforward: “Feral cats also indirectly kill native predators by removing their food base.” [3]

More recently, Guttilla and Stapp seem to prefer Jessup’s take: “Human-subsidized cats… can spill over into less densely populated wildland areas where they reduce prey for native predators (George 1974).” [4]

If any additional work has been done on the subject (surely there are more cats in the area these days; how are the voles and raptors faring?), it seems to have gone unnoticed. Instead, Jessup, Guttilla, and Stapp (and others, too, no doubt) have simply rewritten George’s conclusion to suit their own purposes. Perhaps their version makes for a better story, but it’s rather poor science.

Credit Where Little/None Is Due
When the Lancet recently retracted a 1998 paper linking vaccinations to autism in children—“research” that sparked the ongoing backlash against vaccinations—it was headline news. The move prompted this criticism from one member of the British Parliament: “The Lancet article should never have been published, and its peer review system failed. The article should now be expunged from the academic record…”

At the risk of drawing too many parallels between the two papers, I think the same can be said for Coleman and Temple’s infamous “Wisconsin Study.” (On the other hand, it does serve a useful purpose as a red flag.) Actually, as Goldstein et al. point out, Coleman and Temple’s paper was never peer-reviewed (not necessarily a deal-breaker in my book, but such publications do warrant additional scrutiny), but achieved its mythical status by being cited ad nauseam in peer-reviewed journals, as well as the mainstream media.

Does anybody actually believe the numbers suggested by Coleman and Temple? Stanley Temple (one of the co-authors of the recent anti-feral cat/TNR comment in Conservation Biology) himself admitted their published figures “aren’t actual data; that was just our projection to show how bad it might be.” [5]

I don’t think Longcore et al. [6] or the editors at Conservation Biology put much stock in the Wisconsin Study—so why continue to publish “projections” that have been so thoroughly discredited? Because doing so strengthens their case, at least among those who don’t know any better—especially people outside the scientific community, including many journalists, policy makers, judges, and the general public.

In their recent comment, Lepczyk et al. suggest that conservation biologists and wildlife ecologists “look to the evolutionary biology community” [1] for an example of how to influence policy:

“When local policies or regulations are put forth that promote the teaching of creationism or intelligent design, the evolutionary biologists have responded in force from across the nation and world.” [1]

Let’s set aside for the moment all the baggage associated with their analogy. My question is this: Is the evolutionary biology community still publishing bogus “projections” from 13 years ago? I doubt it.

Check Your Premises
In their recent paper (available for download via the American Bird Conservancy (ABC) website), Dauphiné and Cooper arrive at their absurd figure of “117–157 million free-ranging cats in the United States,” [7] in part, by way of Jessup’s “estimated 60 to 100 million feral and abandoned cats in the United States.” [3]

So where does Jessup’s figure come from? We have no idea—there’s no citation. And Jessup is no authority on the subject—having conducted no studies or reviews of studies that quantify the feral cat population. What’s more, his “estimation” is among the highest figures published. Yet this is the shaky foundation upon which Dauphiné and Cooper attempt to build their subsequent argument.

The authors then add to the (dubious) number of feral cats the proportion of pet cats allowed outdoors. They refer to a 2004 paper by Linda Winter, director of ABC’s Cats Indoors! campaign, in which it was reported, “A 1997 nationwide random telephone survey indicated that 66% of cat owners let their cats outdoors some or all of the time.” [8]

That’s an interesting way to put it—Winter makes it sound like two-thirds of pet cats are essentially outdoor cats. But the surveycommissioned by ABC!—actually indicates that “35% keep their cats indoors all of the time” and “31% keep them indoors mostly with some outside access.” [9] The difference in wording is subtle, and hampered by imprecision—it all comes down to the meaning of some.

Winter’s 2004 paper implies that there are twice as many outdoor pet cats as was indicated in the original survey—an interpretation Dauphiné and Cooper seem to embrace. Had they looked further—and to a less biased source—they might have been able to get a better handle on the degree of outdoor access. For example: a 2003 survey conducted by Clancy, Moore, and Bertone [10] revealing 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.

Do these “part-timers” have the same impact on wildlife as feral cats? Dauphiné and Cooper would have us believe they do.

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

The lesson? Credible research begins with a solid foundation; a weak foundation—one plagued with unsubstantiated claims—on the other hand, leads to pseudoscience.

Or worse. ABC’s Senior Policy Advisor, Steve Holmer, cited Dauphiné and Cooper’s bogus numbers when he spoke to the Los Angeles Times about his organization’s involvement with the legal battle against TNR. It’s like the Wisconsin Study all over again.

When All Else Fails, Look It Up
Though this would seem to be utterly obvious, it apparently bears repeating: Don’t cite work you haven’t actually read.

Isn’t this emphasized in all graduate (indeed, undergraduate, too) programs? What grad student isn’t, at one time or another, tempted to take the easy way out—ride the coattails of somebody else who’s (presumably) done the real work? In addition to the ethical implications, such shortcuts tend to invite more immediate troubles, too. Again, George’s work (described above) provides an excellent case study. Below are some examples of how his work has been referenced in the cat predation literature:

“It is very unlikely that cats bring home all of the prey that they capture. What proportion they bring home has been little studied. George (1974) on a farm in Illinois USA found that three house cats, all adequately fed, brought home about 50% of the prey that they killed.” [11]

“George found that about 50% of prey were indeed brought home, with the other 50% being eaten, scavenged by other animals or simply not found.” [12]

“These approximations are probably underestimates, assuming that cats do not bring back all the prey that they kill.” [13]

Trouble is, George never said these things; what he said was:

“… the cats never ate or deposited prey where caught but instead carried it into a ‘delivery area,’ consisting of the house and lawn. The exclusive use of this delivery area was verified in 18 to 70 mammal captures per cat, as witnessed between early 1967 and 1971.” [2]

In 2000, Fitzgerald and Turner pointed out the fact that George’s work was being misrepresented, noting that the erroneous 50% figure “has been reported widely, though it is unfounded.” [14] Nevertheless, the myth persists—even in 2010.

“In Illinois, George (1974) found that only about half of animals killed by cats were provided to their owners, and in upstate New York, Kays and DeWan (2004) found that observed cat predation rates were 3.3 times higher than predation rates measured through prey returns to owners. Thus, predation rates measured through prey returns may represent one half to less than one third of what pet cats actually kill…” [7]

As Dauphiné and Cooper demonstrate, the “reinterpreted” version of George’s work makes for a very convenient multiplier—suddenly, every kill reported is doubled (or tripled, if Kays and DeWan are to be believed—and they’re not, but that’s a topic for another post). Never mind the fact that it has no basis in actual fact.

Getting a copy of George’s study isn’t difficult, especially with the inter-library loan services available today. To reference it—to use George’s work so that your own appears more credible—without ever having actually read it, is simply inexcusable. But citing it blindly suggests more than laziness—it points to a certain coziness that has no place in scientific discourse. Too much Kool-Aid drinking, and not enough honest research.

*     *     *

Scientists can (and do) look at identical results and come to very different conclusions. But misinterpreting, misrepresenting, or dismissing the conclusions of others, is something else altogether. As the above examples (and there are many, many more!) illustrate, this happens far too often in the feral cat/TNR literature. And if we can’t believe what researchers are saying about the work of others, why would we believe what they say about their own work?

Next, I’ll focus on some of the major flaws in the feral cat/TNR literature—beginning with small sample sizes

References
1. Lepczyk, C.A., et al., “What Conservation Biologists Can Do to Counter Trap-Neuter-Return: Response to Longcore et al.” Conservation Biology. 2010. 24(2): p. 627-629.

2. George, W., “Domestic cats as predators and factors in winter shortages of raptor prey.” The Wilson Bulletin. 1974. 86(4): p. 384–396.

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

4. Guttilla, D.A. and Stapp, P., “Effects of sterilization on movements of feral cats at a wildland-urban interface.” Journal of Mammalogy. 2010. 91(2): p. 482-489.

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

6. 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.

7. 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

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

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

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

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. May, R.M., “Control of feline delinquency.” Nature. 1988. 332(March): p. 392-393.

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

14. 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: Cambridge, U.K.; New York. p. 151–175.