FWS – PDF = WTF

Last Monday, the U.S. Fish & Wildlife Service (FWS) released a draft environmental assessment associated with its Florida Keys National Wildlife Refuges Complex Integrated Predator Management Plan, giving the public 30 days to comment.

Just days later, the document became remarkably difficult to locate, as links to the PDF posted on the FWS website all seem to redirect to the agency’s home page. Later this week, I’ll post my initial impressions of the plan (hint: plan is probably too strong a word for it), but in the meantime, I’ve posted the original document for anybody interested: Download PDF

Revisiting “Reassessment”

“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

2011, Here We Go!

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Season’s Greetings!

Vox Felina Logo—Holiday VersionWarm holiday wishes to the growing network of Vox Felina supporters!

On Invasion and Persuasion

Smithsonian magazine is, according to its website, “created for modern, well-rounded individuals with diverse interests” and “chronicles the arts, history, sciences and popular culture of the times.” Jess Righthand’s recent article, “The World’s Worst Invasive Mammals,” seems—despite its inclusion in the online edition’s “Science & Nature” section—better suited for the pop culture category.

Indeed, the story has more to do with sensationalism than science.

Feral Cat Population
Righthand’s claim that “there are an estimated 60 million feral cats in the United States alone” is conservative compared to some other estimates. David Jessup, for example, suggested in 2004 that there were 60–100 million [1], while, more recently, The American Bird Conservancy Guide to Bird Conservation puts the figure at 60–120 million [2] (neither cites a source).

Still, Merritt Clifton of Animal People, an independent newspaper dedicated to animal protection issues, makes a compelling argument that the population of feral cats in the U.S. is much smaller than is often reported, and may very well be on the decline. [3]

Clifton’s estimates are derived not from surveys of homeowners feeding stray and feral cats, but from “information about the typical numbers of cats found in common habitat types, gleaned from a national survey of cat rescuers… cross-compared with animal shelter intake data.” [4] In 2003, Clifton suggested that “the winter feral cat population may now be as low as 13 million and the summer peak is probably no more than 24 million.” [4]

Predation on Birds
Righthand puts the figure for annual bird deaths attributed to feral cats at “around 480 million.” Nowhere near the “one billion birds” proposed by Nico Dauphine and Robert Cooper, [5] of course, but more than enough to get the attention of Smithsonian readers.

But, as I’ve pointed out repeatedly, even high rates of predation do not equate to population declines (though, clearly, it’s easy to suggest as much). Many researchers have disputed the kind of broad, overreaching claims to which Righthand alludes. Biologist C.J. Mead, for example, reviewing the deaths of “ringed” (banded) birds reported by the British public, suggests that cats may be responsible for 6.2–31.3 percent of bird deaths. “Overall,” writes Mead, “it is clear that cat predation is a significant cause of death for most of the species examined.” Nevertheless, Mead concludes:

“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.” [6]

Mike Fitzgerald and Dennis Turner come to essentially the same conclusion: “We consider that we do not have enough information yet to attempt to estimate on average how many birds a cat kills each year. And there are few, if any studies apart from island ones that actually demonstrate that cats have reduced bird populations.” [7]

Then, too, there’s the critical distinction between compensatory and additive predation—again, a point I’ve made numerous times. Two very interesting studies have generated compelling evidence that birds killed by cats are, on average, significantly less healthy than those killed through non-predatory events (e.g., collisions with buildings). [8, 9] In other words, these birds probably weren’t going to live long enough to contribute to the overall population numbers; predation was compensatory rather than additive.

Public Health Threats
“When house cats are allowed free range outdoors by their owners,” argues Righthand, “or simply don’t have owners, they not only wreak havoc as opportunistic hunters, they can also spread disease. In addition to carrying rabies, 62 to 82 percent of cats in a recent study tested positive for toxoplasmosis.” Here, Righthand seems to be cribbing off of Hildreth, Vantassel, and Hygnstrom, of “Feral Cats and Their Management” fame—hardly a reputable source.

Rabies
Regarding rabies—a topic I’ll save for future posts—I think it’s important to put this into perspective. I happen to have data from Florida handy, and according to that state’s Department of Health, approximately 22,000 Florida residents have died of the flu or pneumonia since 2006 (actually, that figure accounts for only 24 of Florida’s 67 counties, so the total is surely much higher).

By way of comparison: from 2005 through mid-May of this year, there were 11 reported cases of rabies in humans across the entire country (though, I believe there were a handful of reported cases this summer as well).

In terms of public health, then, I think we’re all better off focusing on frequent hand washing, sneezing into our sleeves, and the like—as opposed to, say, exterminating this country’s most popular companion animal by the millions.

Toxoplasma gondii (I)
While it’s true that cats are the definitive host of Toxoplasma gondii, it’s important to note that “wild game can be a source of T. gondii infection in humans, cats, and other carnivores. Serologic data show that a significant number of feral pigs, bears, and cervids are exposed to T. gondii. [10]

“Humans,” write Elmore et al., “usually become infected through ingestion of oocyst-contaminated soil and water, tissue cysts in undercooked meat, or congenitally. Because of their fastidious nature, the passing of non-infective oocysts, and the short duration of oocyst shedding, direct contact with cats is not thought to be a primary risk for human infection.” [11]

But to Righthand’s point: the rate of cats testing positive—or seroprevalence—is, in any event, not a useful measure of their ability to infect other animals or people.

According to Dubey and Jones, “most cats seroconvert after they have shed oocysts. Thus, it is a reasonable assumption that most seropositive cats have already shed oocysts.” [12] “Testing positive,” in this case, is nothing more than the detection of antibodies resulting from seroconversion (the same process, by the way, that takes place in humans after receiving a flu shot).

So, what exactly is Righthand’s point? Did she simply not do her homework here, or is the idea to portray these cats as a threat far, far beyond what the scientific evidence supports? Both, I suspect.

Toxoplasma gondii (II)
T. gondii
, Righthand continues, “has been shown to cause neurological damage to sea otters and other marine mammals that are exposed when heavy rainfall washes infected cat feces into the water.” Again, this is terrain I’ve covered previously. (Righthand, it seems, could do herself—and Smithsonian readers—a favor by subscribing to Vox Felina!)

Yes, T. gondii has been linked to the illness and death of marine life, primarily sea otters [13], prompting investigation into the possible role of free-roaming (both owned and feral) cats. [14, 15] It’s generally thought that oocysts (the mature, infective form of the parasite) are transferred from soil contaminated with infected feces to coastal waterways by way of freshwater run-off. [15]

However, one study found that 36 of 50 sea otters from coastal California were infected with the Type X strain of T. gondii [16], a type linked to wild felids (mountain lions and a bobcat, in this case), but not to domestic cats. [15] A recently published study from Germany seems to corroborate these findings. Herrmann et al. analyzed 18,259 fecal samples (all from pet cats) for T. gondii and found no Type X strain. (It’s interesting to note, too, that only 0.25% of the samples tested positive for T. gondii). [17]

Once again, we’re back to the question: What is Righthand trying to accomplish here?

Population Impacts
“Cats have,” writes Righthand, “also hurt populations of birds, reptiles and other creatures. The black stilt of New Zealand (a seabird), the Okinawa woodpecker and the Cayman Island ground iguana are just a few of the dozens of endangered species at risk due to the proliferation of feral cats.”

At the risk of pointing out the obvious, endangered species are—by definition—at risk due to the proliferation of all sorts of threats. That’s how they became endangered in the first place. To suggest, as Righthand does, that cats are the sole threat these animals face is both misleading and irresponsible.

Righthand (taking a cue, perhaps, from the authors of The ABC Guide?) also makes the common mistake of using island impacts (which are, themselves, more complex than often acknowledged) to imply impacts elsewhere (better yet: everywhere). Readers, it seems, are on their own in terms of doing any research on the topic.

Mission Failure
How much of the blame we can put on Righthand, I don’t know. According to Smithsonian’s website, she’s an intern with the magazine. Had the editors wanted a more thoroughly researched article, they could have demanded one. (This, some readers will recall, is not the first time I’ve been disappointed with the Smithsonian’s lack of rigor.)

According to its website, the mission of the Smithsonian is straightforward but ambitious: “the increase and diffusion of knowledge.” Righthand’s article—misleading at best—falls well short. It seems she’s still struggling with how to best express the organization’s proclaimed values—in this case, going overboard on the creativity at the expense of excellence and integrity.

Literature Cited
1. Jessup, D.A., “The welfare of feral cats and wildlife.” Journal of the American Veterinary Medical Association. 2004. 225(9): p. 1377-1383. http://avmajournals.avma.org/doi/abs/10.2460/javma.2004.225.1377

2. Lebbin, D.J., Parr, M.J., and Fenwick, G.H., The American Bird Conservancy Guide to Bird Conservation. 2010, London: University of Chicago Press.

3. Clifton, M. (2003) Roadkills of cats fall 90% in 10 years—are feral cats on their way out? http://www.animalpeoplenews.org/03/11/roadkills1103.html Accessed May 23, 2010.

4. Clifton, M. Where cats belong—and where they don’t. Animal People 2003 [cited 2009 December 24].  http://www.animalpeoplenews.org/03/6/wherecatsBelong6.03.html.

5. 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. www.pwrc.usgs.gov/pif/pubs/McAllenProc/articles/PIF09_Anthropogenic%20Impacts/Dauphine_1_PIF09.pdf

6. Mead, C.J., “Ringed birds killed by cats.” Mammal Review. 1982. 12(4): p. 183-186. http://dx.doi.org/10.1111/j.1365-2907.1982.tb00014.x

7. 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.

8. 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://dx.doi.org/10.1111/j.1474-919X.2008.00836.x

9. 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/

10. Hill, D.E., Chirukandoth, S., and Dubey, J.P., “Biology and epidemiology of Toxoplasma gondii in man and animals.” Animal Health Research Reviews. 2005. 6(01): p. 41-61. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=775956&fulltextType=RA&fileId=S1466252305000034

11. Elmore, S.A., et al., “Toxoplasma gondii: epidemiology, feline clinical aspects, and prevention.” Trends in Parasitology. 26(4): p. 190-196. http://www.sciencedirect.com/science/article/B6W7G-4YHFWNM-1/2/2a468a936eb06649fde0463deae4e92f

12. Dubey, J.P. and Jones, J.L., “Toxoplasma gondii infection in humans and animals in the United States.” International Journal for Parasitology. 2008. 38(11): p. 1257-1278. http://www.sciencedirect.com/science/article/B6T7F-4S85DPK-1/2/2a1f9e590e7c7ec35d1072e06b2fa99d

13. Jones, J.L. and Dubey, J.P., “Waterborne toxoplasmosis – Recent developments.” Experimental Parasitology. 124(1): p. 10-25. http://www.sciencedirect.com/science/article/B6WFH-4VXB8YT-2/2/8f9562f64497fe1a30513ba3f000c8dc

14. Dabritz, H.A., et al., “Outdoor fecal deposition by free-roaming cats and attitudes of cat owners and nonowners toward stray pets, wildlife, and water pollution.” Journal of the American Veterinary Medical Association. 2006. 229(1): p. 74-81. http://avmajournals.avma.org/doi/abs/10.2460/javma.229.1.74

15. Miller, M.A., et al., “Type X Toxoplasma gondii in a wild mussel and terrestrial carnivores from coastal California: New linkages between terrestrial mammals, runoff and toxoplasmosis of sea otters.” International Journal for Parasitology. 2008. 38(11): p. 1319-1328. http://www.sciencedirect.com/science/article/B6T7F-4RXJYTT-2/2/32d387fa3048882d7bd91083e7566117

16. Conrad, P.A., et al., “Transmission of Toxoplasma: Clues from the study of sea otters as sentinels of Toxoplasma gondii flow into the marine environment.” International Journal for Parasitology. 2005. 35(11-12): p. 1155-1168. http://www.sciencedirect.com/science/article/B6T7F-4GWC8KV-2/2/2845abdbb0fd82c37b952f18ce9d0a5f

17. Herrmann, D.C., et al., “Atypical Toxoplasma gondii genotypes identified in oocysts shed by cats in Germany.” International Journal for Parasitology. 2010. 40(3): p. 285–292. http://www.sciencedirect.com/science/article/B6T7F-4X1J771-2/2/dc32f5bba34a6cce28041d144acf1e7c

American Bird Con

For years now, the American Bird Conservancy (ABC) has been promoting erroneous and misleading information in their tireless effort to vilify free-roaming cats. No organization has been more effective at working the anti-TNR pseudoscience into a message neatly packaged for the mainstream media, and eventual consumption by the general public. Speaking to the Wall Street Journal in 2002, Becky Robinson, co-founder and President of Alley Cat Allies, described ABC’s Cats Indoors! campaign as “a new environmental witch hunt.” [1]

Book Cover: The American Bird Conservancy Guide to Bird Conservation

In their recently released book, The American Bird Conservancy Guide to Bird Conservation, ABC changes tack a bit—using what the authors call “conservative” estimates of the outdoor cat population and annual predation rates, for example, to arrive at their figure of “532 million birds killed annually by outdoor cats.” [2] At the same time, they include much of the same misinformation ABC’s been promoting all along. It’s a clever strategy, really: endorsing bogus claims as valid science without having to defend them as such.

In fact, one doesn’t need to get past the book’s preface before realizing the role that science plays—or, more to the point, doesn’t play—at ABC. “We see very few issues resolved through coming to consensus on the science,” writes President and CEO George Fenwick.

“More often, science divides us. So, though we continue to need excellent science, conservationists also need to learn how to better persuade, use media effectively, and connect birds to the human condition, spirituality and ethical values.” [2]

If its section on cats is any indication, The ABC Guide is the manifestation of Fenwick’s philosophy: more style than substance, more sales than science. The authors didn’t even bother with citations and references, suggesting to readers, perhaps, that The ABC Guide is the last word on the subject. Where free-roaming cats are concerned, though, ABC has precious few answers—in part because they (still) aren’t asking the right questions.

Outdoor Cats
Referring to unattributed 2007 data, the authors of The ABC Guide—Daniel Lebbin, Michael Parr, and George Fenwick—claim that 43 percent of pet cats “have access to the outdoors.” [2] But, according to American Pet Products Association (APPA) 2008 National Pet Owners Survey, 64 percent of cats are indoor-only during the daytime, and 69 percent are kept in at night [3].

Other surveys have yielded similar results, and also indicate that, of those cats that are allowed outdoors, approximately half were outside for three hours or less each day [4, 5]. For Lebbin et al., though, these part-timers are no different from their feral relatives. Of which, “there are 60–120 million,” according to the authors. [2]

Where this figure comes from is anybody’s guess. It’s substantially higher than any other estimates I’ve seen, with one notable exception—a statement made earlier this year by an ABC official (more on that in a moment).

Feral Cat Numbers
Very little exists in terms of credible population estimates for feral cats. There are, however, many unsubstantiated claims.

Among the most popular for those interested in big numbers is the first line from David Jessup’s ironically titled 2004 paper “The welfare of feral cats and wildlife” (ironic because his “concerns” for the welfare of these cats are so plainly disingenuous): “There are an estimated 60 to 100 million feral and abandoned cats in the United States.” [6] As to the origins of Jessup’s “estimate,” again, it’s anybody’s guess, as he offers no reference.

Based on the results of a 1999 telephone survey of Alachua County, Florida, residents, Levy et al. estimated that the population of free-roaming cats represented approximately 44 percent of the county’s total population of cats. [7] Other researchers have reported similar figures for nationwide estimates. [8] By way of comparison, ABC’s estimate represents 39–56 percent of the overall population of cats in the U.S. (based on APPA’s latest figures for pet cats).

On the other hand, Merritt Clifton of Animal People, an independent newspaper dedicated to animal protection issues, makes a compelling argument that the population of feral cats in the U.S. is much smaller than is often reported, and may very well be on the decline. [9] Clifton’s estimates are derived not from surveys of homeowners feeding stray and feral cats, but from “information about the typical numbers of cats found in common habitat types, gleaned from a national survey of cat rescuers… cross-compared with animal shelter intake data.” [10] In 2003, Clifton suggested that “the winter feral cat population may now be as low as 13 million and the summer peak is probably no more than 24 million.” [10]

Population Increase
Earlier this year, ABC’s Senior Policy Advisor, Steve Holmer, told the Los Angeles Times, “The latest estimates are that there are about . . . 160 million feral cats [nationwide].” When pressed for details, Holmer referred me to Nico Dauphine and Robert Cooper’s 2009 Partners In Flight Conference paper. Which, as it turns out, leads right back to ABC and their Cats Indoors! campaign.

Dauphine and Cooper begin their adventure in creative accounting with Jessup’s unattributed 100 million, and add to it the number of owned cats they describe as “free-ranging outdoor cats for at least some portion of the day.” [11] For which they turn to Linda Winter, former director of Cats Indoors!, and her 2004 paper in which she reports the findings of a 1997 telephone survey (commissioned by ABC) of cat owners. According to Winter, “66 percent of cat owners let their cats outdoors some or all of the time.” [12]

In fact, the survey—as reported in ABC’s brochure “Human Attitudes and Behavior Regarding Cats”—indicated that “35 percent keep their cats indoors all of the time” and “31 percent 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), but it’s difficult not to see this as deliberately misleading on Winter’s part.

In any case, results of other surveys (described previously) suggest quite convincingly that outdoor access for the vast majority of pet cats is really very limited. Nevertheless, Dauphine and Cooper persist, arriving at a staggering “117–157 million free-ranging cats.” [11] Holmer, in turn, rounds off the upper limit, “scrubs” the pet cats from the calculation by calling them all ferals, and gets the bogus figure printed in the Times. (Gold star for Holmer!)

Lebbin et al. don’t go that far, but their “most conservative estimate of outdoor and feral cats in the U.S.”—95 million—is, given its shaky origins, no more valid than Dauphine and Cooper’s.

Predation
According to The ABC Guide, “all outdoor cats hunt and kill birds (20­–30 percent of cat prey) and other small animals.” [2] No study I’m aware of has demonstrated that all cats hunt. On the contrary, some research suggests that less than half of outdoor cats hunt. Figures as low as 36–56 percent have been reported by researchers in Australia, for example. [13]

In the UK, Baker, Bentley, Ansell, and Harris reported that 77 cats returned a total of 212 prey items to 52 Bristol households participating in their pilot study, but “in each sampling period, the majority of cats (51–74 percent) failed to return any prey.” [14] The subsequent 12-month study (this time involving 186 Bristol households, 275 cats, and 495 prey items) found a similar level of apparent non-hunters: roughly 61 percent. [15]

Woods, McDonald, and Harris, also working in the UK, found that, although 91 percent of cats returned at least one item, “approximately 20–30 percent of cats brought home either no birds or no mammals.” [16] And Churcher and Lawton’s yearlong “English Village” study (involving approximately 70 cats and 1,090 documented prey items) found that that 8.6 percent of cats brought home no prey [17] (though the authors don’t specify the percentage of cats that returned no birds).

And while it’s true that cats are unlikely to return home with all they prey they catch, it’s equally true that they will bring home items they didn’t kill. Very little is known about the extent of either phenomenon, however. (Carol Fiore’s [18] attempt to unravel this mystery is plagued by methodological missteps and obvious bias; William George’s [19] comments are often interpreted as suggesting that cats return only half of what they catch, though this is incorrect.)

The Diet of Cats
The idea that birds make up 20–30 percent of the diet of free-roaming cats is one that ABC has been promoting since 1997, when they launched Cats Indoors! But it’s no more valid now than it was then.

According to ABC’s brochure, “Domestic Cat Predation on Birds and Other Wildlife” (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.” Ellen Perry Berkeley carefully examined—and debunked—this claim in her book, TNR Past Present and Future: A history of the trap-neuter-return movement, noting that ABC’s 20–30 percent figure wasn’t 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 infamous “Wisconsin Study,” and researchers Mike Fitzgerald and Dennis Turner’s contribution to The Domestic Cat: The Biology of Its Behaviour. [12]

As Berkeley points out, combining or comparing data from these three sources is entirely inappropriate. 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).

To put this into more familiar terms, consider coffee consumption. According to the 2009 National Coffee Drinking Trends Study, 54 percent of American adults drink coffee daily—54, then, is the percentage by frequency. To say that coffee makes up 54 percent of our dietary intake—essentially ABC’s interpretation—is obviously a gross exaggeration of consumption levels. (Neither measure says anything about the supply of coffee, of course.)

Nevertheless, 13 years after ABC first published its report—and six years after Berkeley exposed the error publicly in TNR—the myth persists. So much for ABC’s commitment, spelled out in the book’s section on threats, to “address all of the major threats responsible for killing large numbers of birds, using the best information and research available, while promoting further research and monitoring where it is most needed.” [2]

Which, in turn, raises serious questions about the integrity of ABC and the people running it.

Declawed Cats
Citing Fiore’s thesis research, Lebbin at al. conclude, “de-clawed cats kill as many birds as cats with claws.” [2] Fiore herself is equally confident:

“There were seven declawed cats in the study and all but one took birds (giving a figure of 86 percent); the top predator cat was declawed. Declawing cats appears to have no effect whatsoever on the ability to hunt birds.” [18]

But, both ABC and Fiore leave out some critical details. There were, after all, only 41 cats involved in the study—hardly the kind of sampling required to make such sweeping statements.

A closer look reveals that the declawed cats were apparently responsible for killing an average of 3.6 birds/cat/year while the cats with claws had an average of 3.0. Does this mean that the declawed cats are actually superior hunters compared to the other cats? Hardly.

In addition to the sampling issue, there’s the problem inherent in using the average to describe highly skewed distributions (many cats catching few prey, while few cats catch many prey). In such instances, it’s more appropriate to use median values, which better represent “average” hunting success. [20] Doing so yields estimates of 1 bird/cat/year for the declawed cats vs. 2 birds/cat/year for the cats with claws.

So, declawed cats kill only half as many birds as those with claws? I’ll leave such indefensible claims to others.

Now, to be clear: I’m no advocate of declawing. Nor do I think it’s in the best interest of pet cats to be outdoors—especially those without claws. My point here is merely to demonstrate the flaws in ABC’s deceptively straightforward assertion; once again, ABC is more interested in a good story than they are in good science. (Their comment about declawed cats is precisely the kind of sound-bite that is easily picked up by the media, and repeated so widely that it becomes nearly impossible to trace—never mind untangle.)

Cats and Birds
As evidence of the “variable predation rates by cats,” [2] The ABC Guide refers to just four studies. And, although no citations are included, people familiar with the literature will recognize the numbers and locations immediately.

  1. From Christopher Lepczyk’s dissertation work, the authors somehow extract a figure of 35.5 birds/cat/year, near the low end of Lepczyk’s own estimate of “between 0.7 and 1.4 birds per week.” [21] But Lepczyk’s research suffers from a range of problems—both in terms of his methods and analysis—that inflate his estimated predation rates. (Interestingly, ABC’s Fenwick and Winter are among those Lepczyk thanks “for helpful and constructive reviews” in the Acknowledgements section.)
  2. Another of the predation rates included in The ABC Guide is the more moderate 15 birds/cat/year from Crooks and Soulé’s 1999 paper [22]. But here, too, there are flaws that lead to bloated predation levels.Like Lepczyk, Crooks and Soulé asked residents to estimate annual levels of prey returned home by their cats (in contrast to some studies in which actual prey items are recorded and/or collected). But such guesswork becomes less accurate as estimates increase. David Barratt found that “predicted rates of predation greater than about ten prey per year generally over-estimated predation observed” [20]. At the levels reported by Crooks and Soulé—an average of 56 total prey items (including birds, mammals, etc.) per year—predicted rates were often twice actual predation rates.

    Also, Crooks and Soulé seem (not enough detail is provided in their paper to be certain) to have used a simple average in their calculations, perhaps doubling true predation levels. Taken together, these factors suggest that actual predation levels might be just a quarter of those suggested by Crooks and Soulé.

  3. The third study—easily the most rigorous of the four—with a predation rate of 9.6 birds/cat/year, comes from Woods et al. The researchers, having recruited study participants solely from The Mammal Society, allow that they “may have focused on predatory cats,” and ask that their results be “treated with requisite caution.” [16] They also make clear that their estimated predation rates “do not equate to an assessment of the impact of cats on wildlife populations” [16] (more on that shortly)
  4. Finally, there is the—seemingly inevitable—reference to the Wisconsin Study, though for some reason (again, without explanation) Lebbin et al. have adjusted Coleman and Temple’s figures of 28–365 birds/cat/year downward: “between 5.6 and 109.5.” [2]In this case, the details hardly matter. The Wisconsin Study isn’t actually a study at all; no predation data or findings were ever published. Coleman and Temple’s “estimates”—widely circulated as valid research, thanks in part to ABC—were nothing more than back-of-the-envelope calculations. “Our best guesses,” as the authors themselves admit, “at low, intermediate and high estimates of the number of birds killed annually by rural cats in Wisconsin.” [23]

    “Those figures were from our proposal,” Temple told The Sonoma County Independent. “They aren’t actual data; that was just our projection to show how bad it might be.” [24]

    Sixteen years later, though, ABC is still trying to make “actual data” out of “not actual data.” (Granted, they have backed off from Coleman and Temple’s high estimate, but no mathematical adjustments can transform these flawed, biased guesses into valid research findings.)

Cats as Hunters
Contrary to popular myth, evidence suggests that cats are not quite the hunters they’ve been made out to be. Fitzgerald and Turner suggest that the hunting behavior of cats leads to many “failures,” and, as a result, “many cats soon give up bird hunting altogether.” [25]

“Primarily, all cats hunt both birds and rodents with equal zeal,” observed German zoologist Paul Leyhausen, “and many obviously prefer eating birds.” But, argues Leyhausen (1916–1998), who spent the bulk of his career studying the behavior of cats, “they cannot catch them as easily, and for this reason with increasing experience may soon give up hunting birds.” [26]

“However, our town cats today are often compelled, because of the almost total absence of rodents in their territory to concentrate on chasing birds in order to discharge their pent-up hunting propensities. Even in these circumstances, however, cats are not capable of seriously endangering the songbird population of a substantial area. They almost always catch only old, sick or young specimens. But three quarters of the young birds must perish anyway, since the size of the population in an area remains fairly constant on an average over the years… During years in the field I have observed countless times how cats have caught a mouse or a rat and just as often how they have stalked a bird. But I never saw them catch a healthy songbird that was capable of flying. Certainly it does happen, but, as I have said, seldom. I should feel sorry for the average domestic cat that had to live solely on catching birds.” [26]

Although few predation studies have examined the hunting behavior of cats belonging to managed colonies, those that have are revealing. Reporting on their study of free-roaming cats in Brooklyn, Calhoon and Haspel write: “Although birds and small rodents are plentiful in the study area, only once in more than 180 [hours] of observations did we observe predation.” [27]

Castillo and Clarke, though highly critical of TNR (“This method is not an effective means to control the population of unwanted cats and confirms that the establishment of cat colonies on public lands encourages illegal dumping and creates an attractive nuisance.” [28]), documented little predation in the two Florida parks they used for their study (the focus of which was TNR efficacy, not predation). Over the course of approximately 300 hours of observation (this, in addition to “several months identifying, describing, and photographing each of the cats living in the colonies” [28] prior to beginning their research), Castillo and Clarke “saw cats kill a juvenile common yellowthroat and a blue jay.” [28]

“Cats also caught and ate green anoles, bark anoles, and brown anoles. In addition, we found the carcasses of a gray catbird and a juvenile opossum in the feeding area.” [28]

Another study conducted in a public park, this one in Alameda County, California, also reported low levels of apparent predation of birds (though researcher Cole Hawkins makes every attempt to suggest otherwise). Of 120 scat samples found by searching the “cat area” of Hawkins’ study site, “65 percent were found to contain rodent hair and 4 percent feathers.” [2] This finding comes toward the end of the study, when the cat population was at its greatest (22 were sighted)—and still, only 4 percent contained feathers. And this could easily represent one cat and one bird (and, strictly speaking, even this is not evidence of actual predation, as the bird(s) could have been scavenged).

Impact
To arrive at their figure of “532 million birds killed annually by outdoor cats,” Lebbin et al. multiply “the most conservative predation rate (5.6 birds per cats per year) by the most conservative estimate of outdoor and feral cats in the U.S. (95 million).” [2] They go on to suggest that “the actual number” is “likely… much higher,” [2] though, of course, they ignore or overlook all the errors and misrepresentations bound up in their basic calculation.

Even setting all that aside, the question remains: What impact does predation by cats have on bird populations?

Islands and Continents
Here, the authors focus mostly on the extinction of seabirds linked to the presence of feral cats on islands. I’m only vaguely familiar with the examples they cite, but if the case of the Stephens Island Wren is any indication, the stories are far more complex than ABC suggests. [see, for example, 29 and 30]

But, as Fitzgerald and Turner point out, “because the range of prey available on islands differs markedly from that on the continents the two groups, continents and islands, are treated separately.” [25]

And when it comes to the impact of cats on continental bird populations, ABC highlights rare and endangered species—but ignores entirely two key points. First, as was mentioned previously, even high rates of predation do not equate to population declines.

Referring to the estimated 30 percent of House Sparrow mortality attributed to cat predation in the English Village study, Gary Patronek emphasizes the importance of viewing such predation in the larger context. “When the birds were counted,” writes Patronek, former Director of the Center for Animals and Public Policy at the Cummings School, and one of the founders of the Hoarding of Animals Research Consortium, “they represented the postwinter population prior to hatching of spring chicks. By the year’s end, the actual sparrow population in the village numbered in the thousands, and the 130 birds caught represented about 5 percent of that number.” [31]

Compensatory vs. Additive Predation
Then there is the critical distinction between compensatory and additive predation, something Churcher himself alluded to: “I don’t really go along with the idea of cats being a threat to wildlife. If the cats weren’t there, something else would be killing the sparrows or otherwise preventing them from breeding.” [32]

Two very interesting studies have generated compelling evidence that birds killed by cats are, on average, significantly less healthy than those killed through non-predatory events (e.g., collisions with buildings). [15, 33] In other words, these birds probably weren’t going to live long enough to contribute to the overall population numbers; predation was compensatory rather than additive. Relative to population impacts, then, the “accounting” of bird kills is far more complex than ABC suggests.

Additional Evidence
Many researchers have disputed the kind of broad, overreaching claims Lebbin et al. make about the impact of cats on bird population (and wildlife in general).

Biologist C.J. Mead, reviewing the deaths of “ringed” (banded) birds reported by the British public, suggests that cats may be responsible for 6.2–31.3 percent of bird deaths. “Overall,” writes Mead, “it is clear that cat predation is a significant cause of death for most of the species examined.” Nevertheless, Mead concludes:

“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.” [34]

Mike Fitzgerald and Dennis Turner come to essentially the same conclusion: “We consider that we do not have enough information yet to attempt to estimate on average how many birds a cat kills each year. And there are few, if any studies apart from island ones that actually demonstrate that cats have reduced bird populations.” [25]

In the context of TNR, however, focusing on such figures may be missing the point. “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,” writes Patronek, “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.” [35]

“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 species is an imprecise and contentious process at best. Additional research is clearly needed concerning the welfare of these cats.” [35]

Trap-Neuter-Return
“Many well-intentioned but misguided people,” write Lebbin et al. “exacerbate feral cat problems through a technique called Trap, Neuter, Release (TNR), whereby colony cats are caught, spayed or neutered, and then returned to colonies to be fed by volunteers.” [2] Here, the authors trot out a classic verbal swipe, using the term Release instead of Return, implying a certain lack of planning, or even abandonment (with its legal implications).

They also imply that ABC is a resource for the “misguided.”

Stay Cats (Peep Show)
From The ABC Guide, the caption reads: “Managed feral cat colonies are a hazard to birds and attract the dumping of additional unwanted cats.” In fact, the photographer, Tina Lorien, tells me that these cats were photographed on the Island of Crete, where, it seems, even spayed/neutered pet cats are rather rare.

“Despite its apparent appeal,” Lebbin et al. continue, “few colonies managed under this system shrink, as the program takes more time than most volunteers are able to give, some cats are never caught, and the colonies often become dumping grounds for more unwanted cats.” [2]

Resources
Their claim that TNR programs are ineffective due to limited resources is unsubstantiated. More important, though, they ignore the fact that any feral cat management program is resource-intensive (as is any conservation effort, of course). Several successful TNR programs have been documented (see below), and countless more operate quietly, out of the spotlight.

It’s important to point out, too, that TNR is typically funded through private donations and the out-of-pocket purchases of volunteers. Trap-and-kill, on the other hand, is more likely to rely entirely on local tax dollars.

Sterilization
Their suggestion that all the cats need to be sterilized also lacks support. One often-cited population modeling study—included here more as a reference point than anything else—found that, in order to reduce colony population, approximately 75 percent of fertile cats would need to be sterilized. [36] However, this figure from Andersen, Martin, and Roemer takes into account no adoptions, though the authors point out that adoptions “are similar in effect to euthanasia because these cats are permanently removed from the free-roaming cat population.” [36]

Nor do Andersen et al. consider emigration between cat colonies, though they concede that “a substantial number of owned cats are reported to be adopted strays.” [36] “Substantial” is right—in 2003, Clifton suggested that “up to a third of all pet cats now appear to be recruited from the feral population.” [10]

TNR Successes
Though Lebbin et al. refuse to acknowledge it, TNR has had its share of successes. A 10-year TNR program in Rome, for example, yielded a “16–32 percent decrease on total cat number” across 103 managed colonies. [37] Detractors [38] like to focus on authors’ suggestion that “all these efforts without an effective education of people to control the reproduction of house cats (as a prevention for abandonment) are a waste of money, time and energy.” [37]

In fact, given the 21 percent rate of immigration “due to abandonment and spontaneous arrival,” [37] this colony reduction is quite remarkable. And, as Julie Levy, Maddie’s Professor of Shelter Medicine in the University of Florida’s College of Veterinary Medicine, points out, “such a decline is still beneficial to wildlife if no better alternative is available.” [39] (The “alternatives” ABC proposes—outlined below—are, at best, exactly that: no better.)

Levy, Gale, and Gale reported a 66 percent decline in the population of managed colonies on the University of Central Florida campus between 1991 and 2002, despite the arrival of stray or abandoned cats. [40] (In their paper, Levy et al. cite several other success stories.) And, in their telephone survey of 101 north-central Florida colony caretakers, Centonze and Levy reported “a 27 percent decrease in mean colony size within less than one year of beginning neutering.” [41]

One of the best-known TNR programs is ORCAT, run by the Ocean Reef Community Association, which, according to a 2004 paper, had reduced “overall population from approximately 2,000 cats to 500 cats.” [42] According to the ORCAT website, the population today is approximately 350, of which only about 250 are free-roaming.

Any TNR program contends with the unfortunate (and illegal) dumping of cats. But to suggest that TNR invites abandonment of cats is ridiculous. I’ve seen no research supporting such a claim. If people are determined to abandon their pet cat(s), I fail to see how the presence or absence of a nearby TNR program will affect that decision. On the other hand, cats dumped near a managed colony are far more likely to be adopted and/or sterilized—thereby mitigating their potential impact on the overall population of unowned cats.

Finally, it’s important to note that, although rapid decline—and eventual elimination through attrition—of managed colonies is the goal of TNR (and apparently the only acceptable outcome for the authors of The ABC Guide), reduced growth is not without its benefits. “Population stabilization,” writes Levy, is “a valid metric given that the status quo for unsterilized cats is rapid population growth.” [39]

Alternatives to TNR
Given their ongoing criticism of TNR, one might expect ABC to offer an alternative method of feral cat management—an approach against which to measure TNR (and against which TNR would, presumably, prove inferior). For the most part, though, ABC sidesteps the issue.

“Neutering and spaying pet cats,” write Lebbin et al., “is a humane method for reducing cat over-population.” True enough, but that doesn’t address the sizable population of unowned cats. Although The ABC Guide calls for readers to “make TNR and the feeding of cat colonies illegal,” [2] there’s no recommendation for what should be done with all of these cats.

I put this question to Lebbin and Parr during an ABC webinar celebrating the launch of the book earlier this month. “What we recommend,” said Parr, Vice President of ABC, “as an alternative to [TNR], is not abandoning cats in the first place.” Again, I don’t think there’s any disagreement on this point. Parr continued:

“Other options would be to house those cats in shelters or outdoor sanctuaries which could be managed. Clearly, it’s a huge problem, and the solutions to this are going be things we going to have to work together on for a long period of time, but certainly that would be my first reaction to that question.”

Really, we’re back to sanctuaries? Is this the best ABC has to offer? Almost.

Trap-and-Remove
In their book, Lebbin et al. point out, with obvious pride, that, “By 2004, feral cats had been successfully removed from at least 48 islands worldwide” (there’s another euphemism: removed). [2] A particular “success” is Ascension Island, where, the authors maintain, feral cats had reduced seabird numbers “by 98 percent, from 200 million to 400,000.” [2] As a result of “a multi-year eradication effort that began in 2001,” [2] birds have begun to return.

But, as is often the case, what’s left out of the story is far more interesting than what included.

Detailed accounts of feral cats eradication Marion Island provide a glimpse of the horrors involved. A 1992 paper reports 872 cats shot and 80 more trapped during 14,725 hours of hunting. “Present action” included “mass trapping and poisoning, and the possible use of trained dogs [was] being investigated.” [43] This was after the highly contagious feline panleucopenia virus (feline distemper) had been introduced to the island’s feral cat population, reducing the population by an average 29 percent annually between 1977 and 1982. [44]

On Macquarie Island successful eradication has had “dire” [45] consequences in the form of rapidly increasing rabbit and rodent populations. “In response, Federal and State governments in Australia have committed AU$24 million for an integrated rabbit, rat and mouse eradication programme.” [45]

Given the extent to which conservation efforts backfired on Macquarie Island—less than 50 square miles in size—one can only imagine the consequences and expense (to say nothing of the protests!) of a similar attempt in the continental U.S. But according to ABC, it seems to be either this or sanctuaries—for a population of feral cats they claim to be 60–120 million strong.

(To be fair, Lebbin et al. do offer this concession: “In some cases, invasive or overabundant species may not need to be eradicated, but simply reduced to levels such that they no longer pose a serious threat to native endangered species.” [2] Given their staunch opposition to TNR, however, I suspect this “offer”—which in any case would mean the killing of many millions of cats—does not apply to feral cats.)

The Current Approach
We do have some sense of how ineffective “traditional” feral cat management—a mix of trap-and-kill and inaction—has been. In an interview with Animal Sheltering magazine, Mark Kumpf, President of the National Animal Control Association President from 2007 to 2008, described this approach as “bailing the ocean with a thimble,” suggesting, too, that “the traditional methods that many communities use… are not necessarily the ones that communities are looking for today.” [46]

Clifton goes further, suggesting that trap-and-kill has actually backfired: “Regardless of motive,” writes Clifton, “the effect on the feral cat population replicates natural predation: the most frequent victims are the very young, the old, the disabled, and the ill. The healthiest animals usually escape to breed up to the carrying capacity of the habitat, if they can.” [10]

“Responding to the intensified mortality,” Clifton continues, “felis catus now bears an average litter of four. Nearly seven centuries of killing cats doubled the fecundity of the species.” [10]

Accountability
What Becky Robinson called a “new environmental witch hunt,” [1] I like to think of as a Trojan Horse. Disguised as good advice for responsible cat owners, ABC’s Cats Indoors! campaign has, since 1997, been used more to combat TNR than anything else.

With the publication of The ABC Guide, the authors had a chance to right some past wrongs by coming clean about the research surrounding predation, wildlife impacts, and TNR, as well as the true implications of their call to “make TNR and the feeding of cat colonies illegal.” [2] Instead, they elected for business as usual.

Facts vs. Human Connection
In doing so, ABC missed a golden opportunity to use its enormous influence for moving the discussion forward. (More recently, ABC took another big step backwards by endorsing a deeply flawed and irresponsible paper released by the University of Nebraska-Lincoln, once again sacrificing their integrity for some easy PR.)

But Fenwick, who’s been President and CEO since ABC’s founding in 1994, doesn’t seem to get it. “What have we learned about the opposition?” he asks rhetorically in the book’s preface.

“For one thing, every point of view has its own science and economics to support its contentions, whether it be pro- or anti- pesticide use, free-roaming cats, bird collisions with glass or towers, conflicts with fisheries, land conversion, wind energy, mining, timbering, climate change, or any other issue we consider in addressing bird conservation…” [2]

Fenwick seems to be suggesting that “the opposition” has its own science and economics, whereas ABC has, on its side: Science and Economics (a truly untenable position, in light of a recent ABC press release).

“Facts alone will not win these battles,” he continues, “but human connection might.”

Communication vs. Misinformation
I have to agree with Fenwick that facts alone are insufficient to engage the general public. It’s difficult, for instance, to convey the critical nature of climate change in terms of ocean temperatures rising a couple of degrees Celsius (a figure I use here only to make a point). Explain to people how deep the water may rise in their city or neighborhood, however, and you’re liable to get their attention.

But that’s not what ABC is doing. They have effectively dismissed any and all rigorous science, choosing instead to broadcast as loudly as possible their increasingly dire message—in spite of the science.

Fenwick’s analogy is not climate change, but human health and welfare:

“…no matter the issue, our opposition will unfailingly question our priorities. So, they ask, ‘Why are you blaming __________ when we know habitat loss is the real problem?’ when I am asked these questions, I reply first that we continue to add to our base of knowledge and thus improve decisions affecting bird populations; second, if winning the debate translates to financial gain for the debater, then that position cannot be truly unbiased; and third, isn’t it analogous that if heart disease is the greatest mortality factor in our species, then why do we spend so much money combating cancer and other diseases, poverty and hunger? Solving any single problem—for birds or humans—is insufficient for our cause. Thoughtful people understand that it is critical that we fight for birds and humans across the full, broad front of issues.” [2]

Fenwick’s medical research analogy is an interesting one, but not in the way he intended. Actually, I’m reminded of David Freedman’s profile of John Ioannidis, professor at the University of Ioannina medical school’s teaching hospital, which appeared in last month’s Atlantic. In the piece, Freedman describes a provocative 2005 article that garnered Ioannidis worldwide attention:

“The article spelled out his belief that researchers were frequently manipulating data analyses, chasing career-advancing findings rather than good science, and even using the peer-review process—in which journals ask researchers to help decide which studies to publish—to suppress opposing views.” [47]

Obviously not the image Fenwick was trying to convey—but far more fitting.

Attacking “the full, broad front of issues” simultaneously makes perfect sense, but promoting erroneous and deceptive scientific claims in order to marshal the support necessary is unethical, plain and simple.

We’re not talking about cancer research distracting us from research into heart disease, to use Fenwick’s metaphor. No, what he and ABC are doing—in their relentless persecution of free-roaming cats, at least—is akin to funneling critical resources into the bottling and marketing of snake oil:

There’s no science behind it, and no remedy in its consumption—whatever the dosage.

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43. Bloomer, J.P. and Bester, M.N., “Control of feral cats on sub-Antarctic Marion Island, Indian Ocean.” Biological Conservation. 1992. 60(3): p. 211-219. http://www.sciencedirect.com/science/article/B6V5X-48XKBM6-T0/2/06492dd3a022e4a4f9e437a943dd1d8b

44. Rensburg, P.J.J.v., Skinner, J.D., and van Aarde, R.J., “Effects of Feline Panleucopaenia on the Population Characteristics of Feral Cats on Marion Island.” Journal of Applied Ecology. 1987. 24: p. 63–73.

45. Bergstrom, D.M., et al., “Indirect effects of invasive species removal devastate World Heritage Island.” Journal of Applied Ecology. 2009. 46(1): p. 73-81. http://dx.doi.org/10.1111/j.1365-2664.2008.01601.x

46. Hettinger, J., Taking a Broader View of Cats in the Community, in Animal Sheltering. 2008. p. 8–9. http://www.animalsheltering.org/resource_library/magazine_articles/sep_oct_2008/broader_view_of_cats.pdf

47. Freedman, D.H., Lies, Damned Lies, and Medical Science, in The Atlantic. 2010: Boston. p. 76–86. http://www.theatlantic.com/magazine/print/2010/11/lies-damned-lies-and-medical-science/8269/

Without Apologies

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

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

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

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

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

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

Conversation Killer

Over the weekend, a comment (criticizing, once again, the recently released University of Nebraska-Lincoln “report”) I posted on Audubon magazine’s blog, The Perch, drew fire from Travis Longcore.

Longcore, of course, is the lead author of the widely circulated paper, “Critical Assessment of Claims Regarding Management of Feral Cats by Trap-Neuter-Return” and Science Director for the Urban Wildlands Group, the lead plaintiff in the case that led to the TNR-related injunction in Los Angeles earlier this year (under which City-funded spay/neuter vouchers for feral cats and shelter-based TNR promotions have been halted; TNR, however, continues), a decision currently making its way through the appeal process (I heard just this afternoon that “Round 2” was decided in favor of the plaintiffs).

After a weekend of back-and-forth debate about the science surrounding the UNL report and, more broadly, feral cats and TNR, I posed the following question to Longcore:

You’ve been very straightforward about your desire to see TNR and the feeding of feral cats outlawed. But then what?

I’ve yet to hear from you—or anybody on your side of the issue—spell it out. We all know the cats won’t disappear in the absence of TNR/feeding. We can argue about rates of population growth, carrying capacity, etc.—but let’s keep it simple here. Under your plan, there are these feral cats—an awful lot of them—that no longer have access to the assistance of humans (other than scavenging trash, say). OK, now what?

Will it be like what was done on Marion Island, where—despite being only 115-square-miles in size, barren, and uninhabited—it took something like 16 years to eradicate 2,500 cats? Using disease (feline distemper), poisoning, intensive hunting and trapping, and—if I’m not mistaken—dogs.

And, while we’re at it, who will pay for this unprecedented nightmare?

These are not rhetorical questions. As I say, I’ve heard plenty of arguments against TNR over the past year or so. I’ve yet to hear a single counter-proposal. Not one.

Trap-and-remove? That’s not a proposal—that’s a bromide. I want to hear about how all this would play out. And this seems like an appropriate venue, given the original topic and your role in the L.A. injunction.

So, Travis, what would you do?

Two days later, no word from Longcore. a well-considered reply, but still no answer to the question posed.

Adult Supervision Required III

As I dig deeper into “Feral Cats and Their Management,” I continue to undercover discrepancies between the story Hildreth, Vantassel, and Hygnstrom are telling and what’s actually in the literature.

As I pointed out in my first post on the topic, Olof Liberg did not differentiate between native and non-native prey, as Hildreth, Vantassel, and Hygnstrom suggest. In fact, his reference to “natural prey” [1] was only to distinguish between food provided by humans and any wildlife that cats might consume.

While revisiting Liberg’s paper, though, I found something far more intriguing: it appears Hildreth, Vantassel, and Hygnstrom never made it past the abstract.

In their report, the authors write: “The diets of well-fed house-based cats in Sweden consisted of 15 percent to 90 percent native prey, depending on availability.” [2] But what Liberg is describing here is merely the range of prey brought in by all of the cats in the study, 80–85 percent of which were “well-fed house-based” (the others feral).

Liberg (1984) Figure 1

Moving beyond the abstract, however, the story gets even better. Averaged annually, wildlife makes up just 25–30 percent of the diet of the owned cats (see Fig. 1). Rabbits, being abundant in the area, make up the bulk, with birds—which, we’re made to understand, are of greatest concern for Hildreth, Vantassel, and Hygnstrom—comprising a couple percent at most.

*     *     *

Considering the brevity of the report’s Issues and Impacts section (roughly the same space as was allotted to lethal control methods), the authors managed to squeeze in a surprising amount of misinformation.

Literature Cited
1. Liberg, O., “Food Habits and Prey Impact by Feral and House-Based Domestic Cats in a Rural Area in Southern Sweden.” Journal of Mammalogy. 1984. 65(3): p. 424-432. http://www.jstor.org/stable/1381089

2. Hildreth, A.M., Vantassel, S.M., and Hygnstrom, S.E., Feral Cats and Their Managment. 2010, University of Nebraska-Lincoln Extension: Lincoln, NE. http://elkhorn.unl.edu/epublic/live/ec1781/build/ec1781.pdf

Adult Supervision Required II

In my haste to get my previous post online, I neglected to address a critical point (later brought to my attention by a particularly helpful reader). So, a brief follow-up…

In “Feral Cats and Their Management,” the authors point out—correctly, in this case—that “most feral cats (62 percent to 80 percent) tested positive for toxoplasmosis.” [1] But the rate of cats testing positive—or seroprevalence—is not a useful measure of their ability to infect other animals or people.

According to Dubey and Jones, “Most cats seroconvert after they have shed oocysts. Thus, it is a reasonable assumption that most seropositive cats have already shed oocysts.” [2]

“Testing positive,” in this case, is nothing more than the detection of antibodies resulting from seroconversion (the same process, by the way, that takes place in humans after receiving a flu shot).

And so, any argument for killing feral cats based on their high T. Gondii seroprevalence is deeply flawed (and, it should be obvious, on very shaky ground ethically). According to this line of reasoning, we might well consider quarantining humans testing positive for flu antibodies.

TNR: The Solution, Not the Problem
If T. gondii in feral cats is really the concern, then the focus should be on removing young cats from “high-risk” environments. Sound familiar? That’s a significant part of what TNR programs do.

As Dubey and Jones point out, T. gondii prevalence tends to be higher in feral cats than pet or owned cats. [2] So, getting kittens adopted—a key feature of TNR—reduces the likelihood of their becoming T. gondii “contributors” in the future.

And adoption numbers seem to be significant. In 2003, Merritt Clifton of Animal People, an independent newspaper dedicated to animal protection issues, suggested that “up to a third of all pet cats now appear to be recruited from the feral population.”

One can actually make the argument that TNR—dismissed more or less out of hand by Hildreth, Vantassel, and Hygnstrom—may well be the best defense currently available against the spread of Toxoplasmosis (not only in terms of stabilizing/reducing population numbers overall, but also in that it reduces number of kittens potentially exposed to T. gondii).

Hunting for Scapegoats
Finally, one more interesting note from Dubey and Jones (whose paper is referenced in “Feral Cats and Their Management”):

“In addition to live prey, eviscerated tissues (gut piles) from hunted deer and black bears would be a source of infection for wild cats… Prevalence of T. gondii in wild game and venison in the USA is very high and hunters need to be aware of the risk of transmission of infection to humans and, more importantly, spread of infection in the environment. The viscera of hunted animals need to be buried to prevent scavenging by animals, especially cats.” [2]

But Hildreth et al. prefer to focus (or, take aim, as the case may be) solely on feral cats. Though their motives aren’t clear to me, there’s no doubt whatsoever that they have little understanding of the key issues surrounding TNR—never mind the relevant science.

Literature Cited
1. Hildreth, A.M., Vantassel, S.M., and Hygnstrom, S.E., Feral Cats and Their Managment. 2010, University of Nebraska-Lincoln Extension: Lincoln, NE. http://elkhorn.unl.edu/epublic/live/ec1781/build/ec1781.pdf

2. Dubey, J.P. and Jones, J.L., “Toxoplasma gondii infection in humans and animals in the United States.” International Journal for Parasitology. 2008. 38(11): p. 1257-1278. http://www.sciencedirect.com/science/article/B6T7F-4S85DPK-1/2/2a1f9e590e7c7ec35d1072e06b2fa99d

3. Clifton, M. Where cats belong—and where they don’t. Animal People 2003 [cited 2009 December 24].  http://www.animalpeoplenews.org/03/6/wherecatsBelong6.03.html.

Adult Supervision Required

“Have you seen this already? This is awful.”

That’s what somebody posted on the Vox Felina Facebook page late last night—along with a link to an MSNBC news story. The headline was an attention-getter, no doubt about it: “Report: Kill feral cats to control their colonies.”

But beyond that, MSNBC had practically no details. A little digging around, however, led me to New England Cable News (NECN), which has the complete story.

“The report began in an undergraduate wildlife management class, with students writing reports on feral cats based on existing research. The students’ professor and other [University of Nebraska] researchers then compiled the report from the students’ work.” [1]

“Feral Cats and Their Management” claims, straightforwardly enough, to provide “research-based information on the management of feral cats.” [2] Management, in this case, meaning—as is so often the case in such contexts—killing, extermination, eradication, and so forth. Detailed advice is provided (e.g., “Body-gripping traps and snares can be used to quickly kill feral cats”).

And research? In this case, nothing more than a cursory review of all of the usual suspects: Coleman and Temple, Pamela Jo Hatley, Cole Hawkins, The Wildlife Society, Linda Winter. In other words, lots of Kool-Aid drinking.

It’s Like Science, Only Different
Among the research misinterpreted and/or misrepresented (none of which is cited in the text):

“As instinctive hunters, feral cats pose a serious threat to native wildlife, particularly birds.”

It’s no surprise that the authors of the report offer no evidence to support such a sweeping claim. “There are few if any studies,” write Mike Fitzgerald and Dennis Turner in their contribution to The Domestic Cat: The biology of its behaviour, “apart from island ones that actually demonstrate that cats have reduced bird populations.” [3]

Biologist C.J. Mead, reviewing the deaths of “ringed” (banded) birds reported by the British 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.” Nevertheless, Mead concludes, “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.” [4]

The German zoologist Paul Leyhausen (1916–1998), who spent the bulk of his career studying the behavior of cats, found that cats, frustrated by the difficulties of catching them, “may soon give up hunting birds.” [5]

“During years in the field,” wrote Leyhausen, “I have observed countless times how cats have caught a mouse or a rat and just as often how they have stalked a bird. But I never saw them catch a healthy songbird that was capable of flying. Certainly it does happen, but, as I have said, seldom. I should feel sorry for the average domestic cat that had to live solely on catching birds.” [5]

“Cats kill an estimated 480 million birds per year (assuming eight birds killed per feral cat per year).”

Fitzgerald and Turner (whose work is not referenced in the report) argue that “we do not have enough information yet to attempt to estimate on average how many birds a cat kills each year.” [3] Though, of course, many studies have tried to do exactly that—few, it should be said, involve feral cats.

Unfortunately—and as I have pointed out time and time again—such work typically suffers from a range of methodological and analytical problems (e.g., statistical errors, small sample sizes, and inappropriate/baseless assumptions).

And—as with the UNL report—obvious bias.

“Estimates from Wisconsin indicate that between 500,000 and 8 million birds are killed by rural cats each year in that state…”

How anybody could misquote the numbers from the Wisconsin Study—easily the most widely circulated work on the subject—is a mystery. (On the other hand, the figures were, as Stanley Temple has said, “not actual data” [6] in the first place, so I suppose that does allow for some rather liberal interpretation.)

“The diets of well-fed house-based cats in Sweden consisted of 15 percent to 90 percent native prey, depending on availability.”

How important is it that the prey of feral cats is native, versus non-native? That’s a point of some debate—but not in this case. See, what Liberg actually wrote was this: “Most cats (80-85%) were house-based and obtained from 15 to 90% of their food from natural prey, depending on abundance and availability of the latter.” [7, emphasis mine] He was merely drawing the distinction between food provided by humans and any prey that cats might eat as food.

Liberg goes on to point out that the predation he documented did not, justify a conclusive assessment of the effects of cats on their prey populations, but… indicate[s] that cats by themselves were not limiting any of their prey.” [7] Even high rates of predation do not equate to population declines.

“In California, 67 percent of rodents, 95 percent of birds, and 100 percent of lizards brought home by cats were native species, and native birds were twice as likely to be seen in areas without cats.”

What looks to be truly damning evidence loses much of its impact when it’s seen in context. The reference to Crooks and Soulé’s 1999 paper, for example, omitted the sample size involved: “Identification of 68 prey items returned by cats bordering the fragments indicated that 67% of 26 rodents, 95% of 21 birds and 100% of 11 lizards were native species.” [8] It’s important to note, too, that these researchers asked residents to recall what kind of prey their cats returned—no prey items were collected—thereby raising questions about the accuracy of species attribution.

Furthermore, the cats involved with Crooks and Soulé’s study were all pet cats. How their habits compare with those of feral cats is an open question. Merritt Clifton of Animal People, an independent newspaper dedicated to animal protection issues, suggests, “feral cats appear to hunt no more, and perhaps less, than free-roaming pet cats. This is because, like other wild predators, they hunt not for sport but for food, and hunting more prey than they can eat is a pointless waste of energy.”

The second portion of the quote refers to Cole Hawkins’ PhD dissertation. Hawkins’ research methods and analysis are so problematic that the suggestion of a causal relationship between the presence of cats and the absence of birds (native or otherwise) is highly inappropriate (indeed, Hawkins scarcely investigates predation at all).

Among the key issues: Hawkins had no idea what the “cat” area of his study site was like before the cats were there; he merely assumes it was identical to the “no cat” area in terms of its fauna (though the two landscapes are actually quite different). It’s also interesting to note Hawkins’ emphasis on “the preference of ground feeding birds for the no-cat treatment” while downplaying the fact that five of the nine ground-feeding species included in the study showed no preference for either area. (For a more comprehensive analysis, please see my previous post on the subject.)

“…cats are the most important species in the life cycle of the parasite responsible for toxoplasmosis, and in 3 separate studies, most feral cats (62 percent to 80 percent) tested positive for toxoplasmosis.”

While cats are the “definitive host,” it’s important to note that “wild game can be a source of T. gondii infection in humans, cats, and other carnivores. Serologic data show that a significant number of feral pigs, bears, and cervids are exposed to T. gondii.” [9]

“Humans,” write Elmore et al., “usually become infected through ingestion of oocyst-contaminated soil and water, tissue cysts in undercooked meat, or congenitally. Because of their fastidious nature, the passing of non-infective oocysts, and the short duration of oocyst shedding, direct contact with cats is not thought to be a primary risk for human infection.” [10]

Toxoplasma gondii has been linked to the illness and death of marine life, primarily sea otters [11], prompting investigation into the possible role of free-roaming (both owned and feral) cats. [12, 13] It’s generally thought that oocysts (the mature, infective form of the parasite) are transferred from soil contaminated with infected feces to coastal waterways by way of freshwater run-off. [13]

However, a 2005 study found that 36 of 50 sea otters from coastal California were infected with the Type X strain of T. gondii [14], a type linked to wild felids (mountain lions and a bobcat, in this case), but not to domestic cats. [13] A recently published study from Germany seems to corroborate these findings. Herrmann et al. analyzed 18,259 fecal samples (all from pet cats) for T. gondii and found no Type X strain.  (It’s interesting to note, too, that only 0.25% of the samples tested positive for T. gondii). [15]

[NOTE: Please see follow-up post for additional information about cats and T. gondii.]

“Predation by cats on birds has an economic impact of more than $17 billion dollars [sic] per year in the U.S. The estimated cost per bird is $30, based on literature citing that bird watchers spend $0.40 per bird observed, hunters spend $216 per bird shot, and bird rearers spend $800 per bird released.”

According to this bizarre form of accounting, hunters value an individual bird more than 500 times as much as a birdwatcher does—suggesting, it seems, that dead birds are far more valuable than live birds. This is the kind of estimate that can be developed only through university (or perhaps government) research efforts.

Public Indecency
Stephen Vantassel, a wildlife damage project coordinator who worked on the study, said researchers were aware that some people would be ‘very offended that we offered any type of lethal control method.’ But he said the report was written for public consumption and wasn’t submitted to any science journals for publication.” [1]

For the record, Dr. Vantassel, I’m more offended by the way you’ve allowed such sloppy, grossly irresponsible work to pass for “research.” And the idea that such an undertaking is somehow acceptable because it’s meant for a mass audience is simply absurd!

Naturally, the American Bird Conservancy (ABC) embraced the report immediately, “with one official calling it ‘a must read for any community or government official thinking about what to do about feral cats.’” [1]

“‘Not surprisingly, the report validates everything American Bird Conservancy has been saying about the feral cat issue for many years—namely, TNR doesn’t work in controlling feral cat populations,’ Darin Schroeder, vice president of the Conservation Advocacy for American Bird Conservancy, said Tuesday.”

But validation requires far more than this report provides—beginning with a real interest in scientific inquiry and some basic critical thinking skills. And while we’re at it, a refresher in ethics wouldn’t hurt, either.

*     *     *

In my previous post, I’d indicated that my next post—this post—was going to focus on The American Bird Conservancy Guide to Bird Conservation. Obviously, something came up. Anyhow, the book will keep for a few more days…

Literature Cited
1. n.a. (2010) Report: Kill feral cats to control their colonieshttp://www.necn.com/11/30/10/Report-Kill-feral-cats-to-control-their-/landing_scitech.html?&blockID=3&apID=95afccc4d9564caf8e264f9d087f5732 Accessed December 1, 2010.

2. Hildreth, A.M., Vantassel, S.M., and Hygnstrom, S.E., Feral Cats and Their Managment. 2010, University of Nebraska-Lincoln Extension: Lincoln, NE. http://elkhorn.unl.edu/epublic/live/ec1781/build/ec1781.pdf

3. 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.

4. Mead, C.J., “Ringed birds killed by cats.” Mammal Review. 1982. 12(4): p. 183-186. http://dx.doi.org/10.1111/j.1365-2907.1982.tb00014.x

5. Leyhausen, P., Cat behavior: The predatory and social behavior of domestic and wild cats. Garland series in ethology. 1979, New York: Garland STPM Press.

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

7. Liberg, O., “Food Habits and Prey Impact by Feral and House-Based Domestic Cats in a Rural Area in Southern Sweden.” Journal of Mammalogy. 1984. 65(3): p. 424-432. http://www.jstor.org/stable/1381089

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

9. Hill, D.E., Chirukandoth, S., and Dubey, J.P., “Biology and epidemiology of Toxoplasma gondii in man and animals.” Animal Health Research Reviews. 2005. 6(01): p. 41-61. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=775956&fulltextType=RA&fileId=S1466252305000034

10. Elmore, S.A., et al., “Toxoplasma gondii: epidemiology, feline clinical aspects, and prevention.” Trends in Parasitology. 26(4): p. 190-196. http://www.sciencedirect.com/science/article/B6W7G-4YHFWNM-1/2/2a468a936eb06649fde0463deae4e92f

11. Jones, J.L. and Dubey, J.P., “Waterborne toxoplasmosis – Recent developments.” Experimental Parasitology. 124(1): p. 10-25. http://www.sciencedirect.com/science/article/B6WFH-4VXB8YT-2/2/8f9562f64497fe1a30513ba3f000c8dc

12. Dabritz, H.A., et al., “Outdoor fecal deposition by free-roaming cats and attitudes of cat owners and nonowners toward stray pets, wildlife, and water pollution.” Journal of the American Veterinary Medical Association. 2006. 229(1): p. 74-81. http://avmajournals.avma.org/doi/abs/10.2460/javma.229.1.74

13. Miller, M.A., et al., “Type X Toxoplasma gondii in a wild mussel and terrestrial carnivores from coastal California: New linkages between terrestrial mammals, runoff and toxoplasmosis of sea otters.” International Journal for Parasitology. 2008. 38(11): p. 1319-1328. http://www.sciencedirect.com/science/article/B6T7F-4RXJYTT-2/2/32d387fa3048882d7bd91083e7566117

14. Conrad, P.A., et al., “Transmission of Toxoplasma: Clues from the study of sea otters as sentinels of Toxoplasma gondii flow into the marine environment.” International Journal for Parasitology. 2005. 35(11-12): p. 1155-1168. http://www.sciencedirect.com/science/article/B6T7F-4GWC8KV-2/2/2845abdbb0fd82c37b952f18ce9d0a5f

15. Herrmann, D.C., et al., “Atypical Toxoplasma gondii genotypes identified in oocysts shed by cats in Germany.” International Journal for Parasitology. 2010. 40(3): p. 285–292. http://www.sciencedirect.com/science/article/B6T7F-4X1J771-2/2/dc32f5bba34a6cce28041d144acf1e7c

Framed No. 2

The second in the Framed series is from the recently released book, The American Bird Conservancy Guide to Bird Conservation.

Cats Mating on the Island of Crete

The book’s authors actually have very little to say about TNR, assuming, I suppose, that the accompanying photos say it all. The caption for this one reads (somewhat incongruously, if you ask me): “Managed feral cat colonies are a hazard to birds and attract the dumping of additional unwanted cats.” [1]

Photographer Tina Lorien tells me that these cats were actually photographed on the Island of Crete, where, it seems, even spayed/neutered pet cats are rather rare (never mind managed colonies). Once again, ABC doesn’t let the facts get in the way of a good story (which pretty well summarizes the rest of the book’s section on cats—something I’ll get to in my next post).

*     *     *

On December 2, ABC is hosting a free webinar with book authors Daniel Lebbin, Michael Parr, and George Fenwick—plus novelist and essayist Jonathan Franzen, author of the book’s foreword. Registration is limited to 100 people.

Literature Cited
1. Lebbin, D.J., Parr, M.J., and Fenwick, G.H., Threats: Invasive and Overabundant Species, in The American Bird Conservancy Guide to Bird Conservation. 2010, University of Chicago Press: London.

Framed No. 1

That the ancient Egyptians worshiped cats as gods is, today, common knowledge. Just as their regal little bodies were preserved through mummification, their likenesses were preserved in tomb paintings.

But the cat’s image has not always been portrayed with such reverence. “To the medieval mind,” writes naturalist and biologist Roger Tabor, “there was a sinister side to cat magic, associated with demons and witchcraft. It led to the lowest ebb in the history of the cat.” [1] Naturally, that “sinister side” was depicted in both words and pictures.

Eighteenth century artwork, such as Hogarth’s The Four Stages of Cruelty, suggests that, as Tabor writes, “abuse and torture [of cats] were still widespread.” [1]

And today? Well, it’s a mixed bag. There are the wildly popular LOL Cats, of course, that routinely make their way around the Web. And an astonishing number of photos, illustrations, and videos. (Searching iStockphoto.com for “cats” turns up nearly 40,000 results.)

At the same time, less flattering images seem to be quite popular, too. (“People are rarely neutral about cats,” notes Tabor.) This is hardly surprising; beliefs and attitudes—whatever their origins—rarely change quickly. What is surprising, though, is how some of these images have been employed—at least in some cases—by sources one is expected to take seriously.

I’ve encountered several examples over the course of my research, and have begun “collecting” them for an occasional series of posts, of which this is the first.

Framed No. 1
I don’t recall exactly, but it’s entirely likely that this little gem—from AmmoLand.com, “the webs [sic] leading Shooting Sports News Service for the Ammunition, Firearms, Shooting, Hunting and Conservation communities,” was the one that sparked the idea for the Framed series. Celebrating the injunction earlier this year against publicly funded TNR in Los Angeles, it seems the AmmoLanders got a little carried away.

AmmoLand blog: Cat eating bird

In addition to the poorly rendered dental implants, there’s the erroneous—and rather incomprehensible—caption: “Feral Cats Kill 10,000,000’s of Game Birds & Small Animals Every Month.”

A quick Google search reveals a previous use of the image: New England Birdhouse, a blog devoted to “backyard birding, bird watching, building bird feeders and bird houses, gardening, and New England living.”

Cat Eating Bird

The faux canines are gone, and blogger Bill Askenburg does a better job getting his apostrophes correctly placed. The content itself, though, is no better, as Askenburg has apparently been drinking too much of the American Bird Conservancy’s Kool-Aid.

Finally, a little more digging reveals the original source of the photo, thanks to John Blatchford, a zoology feature writer for Suite101.com, who properly credits Mark Marek Photography.

Literature Cited
1. Tabor, R., Cats—The Rise of the Cat. 1991, London: BBC Books.

Rap(tor) Sheet

Perhaps it’s an act of desperation, this “kitchen sink” approach favored by some free-roaming cat/TNR opponents. Throw everything—including the kitchen sink—into the anti-cat argument, and perhaps something will stick. Their impact on wildlife and the environment, for instance, or their threat to public safety—it seems there’s something for everybody. (Surely it’s only a matter of time before beach erosion, ozone depletion, and climate change are added to this growing rap sheet.)

But for those of us willing to sort through this quantity-over-quality smokescreen, such arguments rarely prove substantive.

I touched on this point in one of my first Vox Felina posts, referring to how the now-classic predation study conducted by William G. George has been misread, misinterpreted, and misrepresented. This work, perhaps more than any other, has been used to suggest an indirect impact of free-roaming cats on raptors.

George was very cautious about drawing such a connection, acutely aware of the speculative nature of his own work. In recent years, however, the details of George’s work—and his well-tempered conclusions—have given way to a kind of mythology, having been co-opted by scientists more interested in their own agendas than in rigorous scientific inquiry.

The Study
Over four years, from January 1, 1968 through December 31, 1971, George monitored and recorded with meticulous care the various small mammals his three cats killed on his “fallow farmland” property in rural Cobden, Illinois. “As predators on rodents,” writes George, “cats inevitably compete for prey with many of our declining raptors, and therein may lie a serious problem.” (emphasis mine) [1].

“I am not suggesting a cause-and-effect relationship exists between the historical increase of cats and the historical decrease of raptors; however, cats, which are as efficient in their way as guns and DDT, accompany and add another dimension to man’s encroachment into wildlife areas.” [1]

The trouble, of course, is that so many scientists citing George’s work have suggested exactly that.

The Myth
“Cat predation on mammals,” write Longcore et al., is “cause for concern because of direct impacts to native species and competition with native predators (George 1974).” [2] “Human-subsidized cats,” warn Guttilla and Stapp, “can spill over into less densely populated wildland areas where they reduce prey for native predators (George 1974).” [3]

Of course anybody who grew up, as I did, watching Wild Kingdom, knows that competition is a central theme of many stories played out in the natural world. But competition for prey is one thing; having an impact on the population of competitors is something else altogether.

Which is precisely what Loyd and DeVore—citing only George’s research—suggest: “Feral cats can also have a considerable impact on the broader health of ecosystems by outcompeting native predators (George 1974)…” [4]

Dauphiné and Cooper, too, interpret George’s work rather loosely, but also seem to offer additional evidence of the indirect impacts about which he speculated:

“In addition to having direct impacts on prey, cats compete with avian predators, such as American Kestrels (Falco sparverius), Northern Harriers (Circus cyaneus), and Redtailed Hawks (Buteo jamaicensis) (George 1974, Mosher 1989, Lepczyk et al. 2004). George (1974) estimated that cats killed 5.5 million rodents and other vertebrates in a 26,000 square mile area in Illinois, effectively depleting the prey base for wintering raptors and other native predators.” [5]

What did Lepczyk add to the conversation? Nothing, actually; he merely cited George’s study:

“… cats may be directly competing with avian predators, such as American Kestrels (Falco sparverius), Northern Harriers (Circus cyaneus) and Red-tailed Hawks (Buteo jamaicensis; George, 1974).” [6]

And Mosher? This one’s far more interesting. According to Dauphiné and Cooper, Mosher’s research reveals some compelling evidence:

“In a study in Maryland of Cooper’s Hawks (Accipiter cooperii) that depended heavily on eastern chipmunks (Tamias striatus) to feed nestlings, Mosher (1989) found that these raptors altered their diet to prey more on songbirds in an area where chipmunks were eradicated by cats. The resulting increase in hunting time and difficulty for Cooper’s Hawks was associated with a decrease in nestling survival.” [5]

But Mosher’s paper includes no mention of cats at all. In fact, he suggests only “that reproductive performance, especially in studies encompassing relatively small areas, may reflect natural phenomena such as dependence on a particular prey species that undergoes population fluctuations.” [7] I found an earlier paper by Mosher, also mentioning chipmunks and Cooper’s Hawks [8]—but again, no mention of cats.

It’s possible this is an honest mistake, that Dauphiné and Cooper merely included the wrong reference. However, I was unable to find a hint of any such research in my (admittedly brief) online sleuthing. And, given the sloppiness and bias that permeates the rest of their paper, nothing these two might do would surprise me.

(If, as Dauphiné and Cooper suggest, the real problem is that raptors are preying on songbirds rather than chipmunks, then shouldn’t we be doing everything in our power to increase the chipmunk population? It’s an absurd suggestion, of course—but only slightly more so than many accepted wildlife “management” practices.)

Getting back to George’s research, the winner for most distorted version undoubtedly goes to David Jessup, who writes with a certitude generally reserved for politicians, marketers, and novelists. Gone is the trepidation 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.” [9]

Local/Regional Raptor Update
So, how have those raptors fared in the subsequent 40 years? Certainly there are factors other than cats that would likely contribute to their decline—habitat fragmentation and destruction, for instance. Such environmental impacts have the potential to affect the birds themselves, clearly, but also their prey.

Research into the population trends of Red-tailed Hawks, Northern Harriers, and American Kestrels—three raptors identified specifically by George—suggests that his concerns were largely unfounded.

BBS Routes and Data
Only one Breeding Bird Survey (BBS) route runs into Union County, Illinois, where George’s property was located. Unfortunately, count data for BBS Route 34080 go back only to 1993. However, data for neighboring routes are available from the time of George’s study through 2006. Surveys along two nearby routes in Illinois (34059 and 34061) began in 1970; surveys of two others, along the eastern edge of Missouri (52001 and 52007), date back to 1967.

Selected BBS Routes: Missouri and Illinois

No BBS count data from the routes in question are available for Northern Harriers, suggesting that perhaps this species was, for one reason or another, simply not included. Data sets for other birds—the Red-shouldered Hawk, for example—exist despite frequent counts of zero (in the case of the Red-shouldered Hawk, just one bird was recorded along Routes 52001 from 1967 through 2006).

BBS data for Red-tailed Hawks indicate a rather dramatic population increase for the two southwestern Illinois routes, and slight increases for the same period across the two eastern Missouri routes, as indicated in the following graphs.

Red-tailed Hawks Four BBS RoutesBBS Data: Red-tailed Hawks for two Illinois and two Missouri routes (adapted from North American Breeding Bird Survey website)

Populations of American Kestrels (along the same routes and for the same period) remained mostly stable.

American Kestrels Four BBS RoutesBBS Data: American Kestrels for two Illinois and two Missouri routes (adapted from North American Breeding Bird Survey website)

The bottom line? If the area’s cats are out-competing the raptors for prey, there’s no evidence in the BBS count data.

Prairie Voles
Of particular interest to George were prairie voles, which made up “more than 41 percent of all captured vertebrates and 45 percent of the captured mammals.” [1] And whose reduced numbers, suggested George, “could well pose the principal threat to the success of wintering hawks in my area of study.” [1] But maybe the voles weren’t as important as George surmised.

In Minnesota, the declining population of prairie voles—significant enough to warrant “special concern species” status beginning in 1984—seems to have had no effect on the populations of Northern Harriers, Red-tailed Hawks, and American Kestrels. Indeed, BBS data indicate that these raptors’ numbers have fluctuated little over the past 40 years or so. (And, according to the Minnesota Department of Natural Resources, the reason for the state’s declining vole numbers has nothing to do with cats, but “is due almost exclusively to the destruction of its prairie habitat through plowing and over-grazing.”)

BBS Data: Three Raptors across MinnesotaBBS Data: Three raptor species across Minnesota (adapted from North American Breeding Bird Survey website)

Raptors Across the Country
Of course, isolating the relationship between the population of a predator and that of its preferred prey species is incredibly difficult; there are simply too many additional—often interdependent—factors that must be considered. Zooming out for a big-picture view of population dynamics across the U.S. only blurs such relationships, thereby complicating any subsequent analysis.

Nevertheless, I think it’s worth a look. George claimed (unfortunately, without referring to a specific source, and without specifying whether he was referring only to owned/pet cats) that there were 31 million cats in the U.S. at the time of his study. [1] Today, according to the American Pet Products Association’s 2009–2010 National Pet Owners Survey, there are 93.6 million.

Direct comparisons over this 40-year time frame are difficult for a number of reasons (e.g., lack of reliable data, the increasing proportion of indoor-only cats in recent years, etc.). But if, as some suggest, cats are having an negative impact on raptor populations—and there are now three times as many of them (not accounting for feral cats, whose numbers have also likely increased)—well, one might expect find these birds in dire straights by now.

Hawk Mountain Sanctuary
To see for myself, I turned to Hawk Mountain Sanctuary’s Conservation Status Reports. Located in east-central Pennsylvania, Hawk Mountain Sanctuary is, according to its website, “the world’s first refuge for birds of prey.”

The outlook for the Northern Harrier and Red-tailed Hawk is mostly good. “The Northern Harrier is considered secure in most of North America,” notes its 2007 conservation report, “but it is a species of concern regionally in many of the [Bird Conservation Regions] west of the Mississippi River.”

The Red-tailed Hawk, too, “is considered secure throughout most of its range in North America.

“Migration counts have declined in eastern North America since 1995, but concurrent increases in [Breeding Bird Surveys] and [Christmas Bird Counts] suggest that these migration trends may be the result of changes in migration geography or behavior. Elsewhere in North America, population monitoring generally indicates increasing or stable populations of this common raptor.”

American Kestrels, on the other hand, seem to be in trouble: “Overall, the data suggest substantial declines in populations… across much of North America, and consequently strong cause for conservation concern.” The factors affecting these declines are unknown and, the report notes, “warrant further investigation.” However, some patterns have been observed—“factors exerting negative influences on populations are strongest along the Atlantic coast,” for example. Also: “More recent declines in western North America… appear to have occurred in concert with a prolonged drought.”

The Cornell Lab of Ornithology’s website paints a rather different picture, noting that the population of American Kestrels “increased greatly with historical deforestation of North America. No significant trend across North America, but some local increases and decreases.”

*     *     *

All of which adds up to… what? Like the BBS data, the Hawk Mountain Sanctuary Conservation Status Reports reveal population trends perhaps best described as “mixed.” Nowhere is there any indication that declining raptor numbers can be linked to the success of competing predators—including cats.

For George, the idea was nothing more than a hypothesis anyhow. But rather than put it to the test (ostensibly the role of scientists), Longcore, Dauphiné, Jessup, and the rest, have instead tried to elevate its status through nothing more than repetition—thereby betraying an agenda that has little to do with science at all.

Literature Cited
1. George, W., “Domestic cats as predators and factors in winter shortages of raptor prey.” The Wilson Bulletin. 1974. 86(4): p. 384–396. elibrary.unm.edu/sora/Wilson/v086n04/p0384-p0396.pdf

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. 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. http://dx.doi.org/10.1644/09-MAMM-A-111.1

4. Loyd, K.A.T. and DeVore, J.L., “An Evaluation of Feral Cat Management Options Using a Decision Analysis Network.” Ecology and Society. 2010. 15(4). http://www.ecologyandsociety.org/vol15/iss4/art10/

5. 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. www.pwrc.usgs.gov/pif/pubs/McAllenProc/articles/PIF09_Anthropogenic%20Impacts/Dauphine_1_PIF09.pdf

6. 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. http://www.sciencedirect.com/science/article/B6V5X-48D39DN-5/2/d27bfff8454a44161f8dc1ad7cc585ea

7. Mosher, J.A., Accipiters, in Northeast Raptor Management Symposium and Workshop, B.A.G. Pendleton, Editor. 1989, National Wildlife Federation Scientific and Technical Series No. 13.: Syracuse, NY. p. 47–52.

8. Mosher, J.A., “Breeding Biology of Raptors in the Central Appalachians.” Raptor Research. 1982. 16(1): p. 18–24.

9. Jessup, D.A., “The welfare of feral cats and wildlife.” Journal of the American Veterinary Medical Association. 2004. 225(9): p. 1377-1383. http://avmajournals.avma.org/doi/abs/10.2460/javma.2004.225.1377

A Tale of Two Cities

Gray Catbird (Dumetella carolinensis)A Gray Catbird in Madison, Wisconsin, USA. Photo courtesy Wikimedia Commons and John Benson.

According to its website, the Smithsonian Migratory Bird Center is a “national and international leader in the biology and conservation of migratory birds.” When it comes to cats and their potential impact on birds, however, the SMBC apparently has a lot to learn.

Actually, they could use some pointers on professionalism, too—and maybe a refresher on the difference between correlation and causation.

Summarizing a recent study of gray catbird fledglings in the Washington, DC area, the SMBC claims that cats were responsible for “alarmingly high rates of nest predation and fledging [sic] mortality.” But there’s no mention of how such a connection was made. Indeed, “Baby Catbird Survival” offers very little in the way of details. Instead, readers are treated to sophomoric commentary:

“… several guilty-looking cats were found in close proximity to dead birds. Our guess is that closer examination would have revealed feathers in their whiskers.”

This is the Smithsonian? What I wouldn’t give to have been in the marketing meeting where “predation humor” was first proposed as an innovative, sure-fire scheme for attracting new donors and research funding.

Catbird Mortality
The study, spanning two summers, was conducted at three sites, two in Takoma Park, MD, and another—apparently less populated with cats—in Bethesda, MD. Somehow—again, no details are given—radio-tracking technology was used to monitor the mortality of young catbirds.

Results indicate that 85% of nests at the Bethesda site were “successful” (i.e., young catbirds survived long enough to leave the nest), compared to only 34% of nests at the Takoma Park sites. At the Bethesda site, 29% of fledglings survived to eight weeks of age, versus 14% at Takoma Park.

Given the rather dramatic nature of these findings, one might expect some explanation of the research methods and analysis techniques employed. Among the numerous questions left unanswered:

  • How was radio-tracking used to distinguish predation from other forms of mortality—or, more to the point, predation by cats from other forms of predation?
  • How were the sites selected, and the cats at each site counted?
  • What other factors (e.g., population density of humans, abundance of other predators, habitat availability and condition, etc.) might have been at work here?
  • What were the sample sizes employed?

At best—and this is being very generous—the results suggest correlation. But, of course, this is very different from causation.

In Proofiness, author Charles Seife uses the relationship between a country’s energy consumption and the life expectancy of its citizens to illustrate the difference. Plot the data and there is an unmistakable trend: as energy consumption increases, so does life expectancy.

“Yes, it’s true that the more power a society uses, the longer its citizens live, on average. It’s equally true, however, that the more garbage a society produces, the longer its people live. The more automobiles people in a society drive, the more newspapers people in a society read, the more fast food people consume, the more television sets people have, the more time people spend on the Internet…” [1]

So, are the Takoma Park cats the cause of catbird mortality? Who knows.

Who’s In Charge?
Exactly who’s responsible for “Baby Catbird Survival” is another mystery (though anonymity is understandable in this case, as it’s difficult to imagine any respectable scientist claiming ownership of something so flimsy and irresponsible). The researcher who oversaw the project, though, is Peter Marra, the SMBC scientist at the center of a recent Washington Post column (of which I was highly critical).

This, of course, is the same Peter Marra who, along with nine of his colleagues, has argued that “trap-neuter-return is essentially cat hoarding without walls,” and called for “legal action against colonies and colony managers.” [2] The authors also call on conservation biologists to “begin speaking out” against TNR “at local meetings, through the news media, and at outreach events.” [2] It’s a message Marra has obviously taken to heart.

There’s no doubt Marra has an agenda. The question is: how might this bias his research?

Untangling the Research
With so few details to go by, it’s difficult to scrutinize Marra’s catbird study. If it’s published, of course, greater transparency will be required. In the meantime, we do have some useful clues that—along with a little detective work—provide some insight.

Counting Cats
As I indicated previously, it’s hard to imagine that the only difference between the Takoma Park and Bethesda sites was the number of cats. Even if that were the case, though, absolute numbers are hardly the whole story. Numerous studies have demonstrated that predation success varies widely among domestic cats: some catch lots of prey while others catch very few—or none at all. [3–7]

That’s assuming they can get at the prey, of course.

Marra is clear in the Post piece that the (alleged) killers “aren’t feral cats; they’re domestic cats allowed to go outside.” But, contrary to what columnist Adrian Higgins suggests, studies have shown that about two-thirds of cats are indoor-only. [8–11] And of those allowed outside, approximately half spend less than three hours outdoors each day. [9, 10]

How sure can Marra be, then, that the areas’ pet cats are responsible for the deaths of young catbirds?

Predatory Habits
The author of “Baby Catbird Survival” claims that “domestic cats typically only decapitate birds and leave the carcass.” Now, I’ve become quite familiar with the research on the hunting behavior of cats over the past year or so, and recall seeing nothing to this effect. I recently revisited some key sources [12–15] just to be sure, and again found nothing to support this assertion. However, it was brought to my attention that some birds will decapitate their prey:

“In urban and suburban settings grackles are the most likely culprits, although jays, magpies, and crows will decapitate small birds, too. Screech-owls and pygmy-owls also decapitate their prey, but, intending to eat them later, they usually cache their victims out of sight.” [16]

“There is little you can do to discourage screech-owls if only because they do their killing under cover of darkness. However, you can recognize their handiwork by looking for partially plucked carcasses of songbirds with the heads missing… Corvids—crows, ravens, jays, and magpies—are well known for their raids on birds’ nests to take eggs and nestlings.” [17] (Interestingly, the author, David M. Bird, was among Marra’s nine co-authors on “What Conservation Biologists Can Do.”)

Again, how can Marra be so sure the cats are the culprits?

Catbird Population
And finally, what about Marra’s claim, as reported by Higgins, that “catbirds in cat-heavy areas are not able to reproduce at a rate that is sustainable”?

Data from the North American Breeding Bird Survey suggest that Maryland’s gray catbird population declined perhaps 7% between 1966–1989, a period during which the state’s human population grew approximately 35%.

BBS Data: Catbirds Across MarylandBBS Data: Gray Catbirds Across Maryland (adapted from the Atlas of the breeding birds of Maryland and the District of Columbia)

Even so, the Atlas of the Breeding Birds of Maryland and the District of Columbia—which includes the aforementioned BBS data in its assessment—reports that, “during the Atlas period [1983–87], gray catbirds were found throughout the state, including the most heavily urbanized blocks.” The Atlas goes on to note the bird’s “high tolerance for human activity,” concluding that “the gray catbird’s future in Maryland seems secure.” [18]

Indeed, the SMBC itself echoes the Atlas’ assurances:

“To thrive in these [fragmented] habitats birds must have special adaptations such as the ability to respond to frequent nest predation and parasitism and to forage on a wide variety of seasonally available foods. Armed with these adaptations, catbirds are well prepared for the disturbed habitats of the 21st century’s fragmented landscape.”

Still, statewide figures such as those complied in the Atlas can obscure as much as they reveal. Better to look at the detailed counts from individual survey routes. And it turns out data from BBS Route 46110, the nearest to the Takoma Park and Bethesda sites, actually trend upward in recent years. (Note: It’s important to point out that “the survey produces an index of relative abundance rather than a complete count of breeding bird populations.”)

BBS Data: Gray Catbirds Along Route 46110BBS Data: Gray Catbirds Across Route 46110 (adapted from North American Breeding Bird Survey website)

All of which has me wondering about Marra’s rather dire forecast for the area’s gray catbirds—in terms of the underlying science, of course, but also the possible motives behind such a statement.

*     *     *

Publishing dodgy science within the scientific community is one thing—hardly excusable, but there is at least a reasonable expectation that one’s peers are in a position to critically evaluate such research—but to package this kind of work for public consumption is truly irresponsible. Like Higgins’ column, “Baby Catbird Survival” is a Trojan Horse: unsubstantiated—and, potentially, highly damaging—claims “wrapped up” as valid science.

Brilliant from a marketing standpoint, maybe—but it’s hardly my idea of leadership.

I’ve attempted to contact both the SMBC and Peter Marra—expressing my concerns with “Baby Catbird Survival,” but also my interest in a more complete accounting of the study’s findings. Unfortunately, neither has responded.

SPECIAL THANKS once again to Louise Holton and Maggie Funkhouser at Alley Cat Rescue for bringing the Washington Post article to my attention.

Literature Cited
1. Seife, C., Proofiness: The Dark Arts of Mathematical Deception. 2010: Viking Adult.

2. 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.

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

4. Woods, M., McDonald, R.A., and Harris, S., “Predation of wildlife by domestic cats Felis catus in Great Britain.” Mammal Review. 2003. 33(2): p. 174-188.

5. 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.

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. 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.

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

9. 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.

10. Lord, L.K., “Attitudes toward and perceptions of free-roaming cats among individuals living in Ohio.” Journal of the American Veterinary Medical Association. 2008. 232(8): p. 1159-1167.

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

12. Tabor, R., Cats—The Rise of the Cat. 1991, London: BBC Books.

13. Leyhausen, P., Cat Behavior: The predatory and social behavior of domestic and wild cats. Garland series in ethology. 1979, New York: Garland STPM Press.

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.

15. Turner, D.C. and Meister, O., Hunting Behaviour of the Domestic Cat, in The Domestic Cat: The Biology of Its Behaviour, D.C. Turner and P.P.G. Bateson, Editors. 1988, Cambridge University Press: Cambridge.

16. Thompson, B., The Backyard Bird Watcher’s Answer Guide. 2008: Bird Watcher’s Digest.

17. Bird, D.M., Crouching Raptor, Hidden Danger, in The Backyard Birds Newsletter. 2010, Bird Watcher’s Digest.

18. Robbins, C.S. and Blom, E.A.T., Atlas of the breeding birds of Maryland and the District of Columbia. Pitt series in nature and natural history. 1996, Pittsburgh, PA: University of Pittsburgh Press.

Inside Job II

Another study demonstrates that the majority of pet cats spend their time indoors.

In my previous post on the subject, I somehow overlooked Linda Lord’s paper, “Attitudes toward and perceptions of free-roaming cats among individuals living in Ohio.” [1] In it, Lord, Assistant Professor in Ohio State University’s College of Veterinary Medicine, presents the results of an extensive 2007 telephone survey.

Fifty-nine percent of the 217 cat owners participating in the study reported that their cats were indoor-only. Nearly 20% more allowed their cats outdoors no more than three hours each day.

Linda Lord Indoor-Outdoor Data

Lord’s results are very much in line with findings from the three studies I cited previously. [2–4] All of which contradict the bogus claims made recently by Washington Post columnist Adrian Higgins, and last year by Nico Dauphiné and Robert J. Cooper (download their Partners in Flight conference paper here). [5]

These findings also raise questions about a comment made by Pete Marra in the Post story. Referring to his recent investigation into the mortality of catbird fledglings, Marra suggests that the culprits “aren’t feral cats; they’re domestic cats allowed to go outside.” I’ll take a closer look at Marra’s study in my next post…

Literature Cited
1. Lord, L.K., “Attitudes toward and perceptions of free-roaming cats among individuals living in Ohio.” Journal of the American Veterinary Medical Association. 2008. 232(8): p. 1159-1167.

2. 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.

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

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

5. 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. www.pwrc.usgs.gov/pif/pubs/McAllenProc/articles/PIF09_Anthropogenic%20Impacts/Dauphine_1_PIF09.pdf

National Feral Cat Day

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

Garden Tool

The timing was uncanny. Four days after my post “Inside Job,” Washington Post columnist Adrian Higgins reported incorrectly that two-thirds of pet cats are allowed outdoors. Higgins doesn’t mention where he got that figure, but considering the sources he used for the piece—including the American Bird Conservancy (ABC), The Wildlife Society, and Dauphiné and Cooper’s 2009 Partners in Flight paper—it’s not hard to sort out.

Ditto for his matter-of-fact assertion that “the cumulative effect on birds is significant, according to experts.” Higgins relies on Dauphiné and Cooper for estimates of both the number of “stray and out-and-out feral cats” (“there may be as many as 100 million such cats in the country”) and birds killed by free-roaming cats (“at least one billion birds are killed by cats annually, ‘and the actual number is probably much higher.’”). [1]

Higgins’ column appeared exactly one week after the release of Charles Seife’s book Proofiness: The Dark Arts of Mathematical Deception. Proofiness, writes Seife, is “the art of using bogus mathematical arguments to prove something that you know in your heart is true—even when it’s not.” [2]

Many—perhaps most—of the scientific claims made by opponents of free-roaming cats/TNR are textbook cases of proofiness. Nevertheless, they are often accepted at face value by the media, which—simply by passing them along for public consumption—gives these assertions unwarranted credibility.

Pete Marra
The central character in Higgins’ story is Pete Marra, a fellow gardener and a research associate at the Smithsonian Conservation Biology Institute. Marra’s name rang a bell.

Sure enough, this is the same Peter P. Marra who, along with nine others (including Dauphiné and Cooper), authored a comment in Conservation Biology earlier this year, entitled “What Conservation Biologists Can Do to Counter Trap-Neuter-Return: Response to Longcore et al.” (the publication of which prompted a series of Vox Felina posts, beginning with this one).

What Marra and his co-authors penned is an unapologetic call to action:

Proponents of TNR are well organized and push for TNR-friendly policies in communities and shelters around the United States, often with little opposition from the conservation biology and wildlife ecology communities… Regardless of why the scientific and management communities have remained relatively silent, it is imperative that we now begin speaking out. [2]

As I have argued, the silence that so frustrates Marra and the others may simply reflect the fact that so much of the work he and his colleagues defend is largely indefensible. Indeed, “What Conservation Biologists Can Do” is, in its own way, representative. Consider the authors’ comparison of TNR with hoarding:

The animal welfare community opposes “cat hoarding,” whereby people care for more pets than they can adequately support, because it is considered inhumane. Trap-neuter-return is essentially cat hoarding without walls. Considering that most communities have laws banning animal hoarding, we should consider the same standard for outdoor cats as those that are in a person’s home. [3]

But their interest in using the law to put a stop to TNR doesn’t end there. Marra and his colleagues continue:

…it may become incumbent upon us to take legal action against colonies and colony managers, particularly in areas that provide habitat for migratory birds or endangered species. [3]

The authors quote a 2003 article written by Linda Winter, the former director of the ABC’s Cats Indoors! campaign, for the Hawaii Audubon Society newsletter:

“…releasing cats into the wild and supporting feral cat colonies is a violation of the Migratory Bird Treaty Act and the Endangered Species Act, as well as laws prohibiting animal abandonment.” (her emphasis, not mine) [4]

As a frequent critic of Winter’s writing, I was eager to read the newsletter (which can be downloaded here). It turns out Winter was referring to a 2003 report submitted by Pamela Jo Hatley—then a student in the University of Florida’s Levin College of Law and part of its University of Florida Conservation Clinic—to the U.S. Fish & Wildlife Service.

Winter—and by extension, Marra and his colleagues—are unambiguous on this point: TNR is a clear violation of both the Migratory Bird Treaty Act and the Endangered Species Act. But, of course, law students don’t make legal decisions; that’s what we have courts for (which might explain why, years later, Travis Longcore and his Urban Wildlands Group took a rather different approach in their TNR-related lawsuit against the City of Los Angeles).

But back to Hatley—there’s another familiar name. In fact, I’d seen it right beside Marra’s earlier this year. See, Pamela Jo Hatley is one of the 10 co-authors of “What Conservation Biologists Can Do.”

So why didn’t the authors just cite Hatley’s work directly, rather than turning to Winter’s version of it? Simply put, Winter’s version is a better story—short and sweet, and brimming with certitude.

But if Marra and the others—Hatley included—wanted to distance themselves from the original, it’s understandable. Though her legal arguments are somewhat compelling, Hatley’s report is a minefield of misrepresentations, flawed estimates, and unsubstantiated claims where the science is concerned (e.g., extrapolating the Wisconsin Study to Florida, and then suggesting that “the actual number [of birds killed by cats in the state] may be much higher” [5]). In other words, more proofiness.

Its title, Feral Cat Colonies in Florida: The Fur and the Feathers Are Flying, is a good indication of how seriously the report—ostensibly a formal document submitted to a federal agency—should be taken.

Getting Dirty
To read Higgins’ column in the Post, one gets the idea that he and Marra are merely fellow gardeners, perhaps having bumped into each other at the local nursery or hardware store. And that’s where the story began. It could be.

But there’s a sentence in “What Conservation Biologists Can Do” that’s been bothering me ever since I read Higgins’ piece:

Conservation biologists have just as much opportunity to make their points at local meetings, through the news media, and at outreach events as do TNR proponents. (emphasis mine) [2]

I have no idea whether Higgins and Marra knew each other before Higgins began work on his column, or how Higgins feels about cats. And I’m not one to go in for conspiracy theories, either.

What I am sure of is that Higgins—as a journalist—should have done his homework. He did not. (To be fair, Higgins did speak with Alley Cat Allies; but “equal time” is a poor substitute for accuracy.) And the consequences of his carelessly scattering a few figures around a column devoted to gardening are considerable: the seeds of proofiness!

Maybe readers don’t expect Higgins to know (or care, even) how many free-roaming cats there are in the U.S. Or how much time pet cats spend outdoors. Still, though, Higgins is an avid gardener—he, of all people, should be able to recognize bullshit.

*     *     *

SPECIAL THANKS to Louise Holton, founder of Alley Cat Rescue, who brought the Washington Post article (along with countless other news items over the past few months!) to my attention. She and Maggie Funkhouser, ACR’s Director of Communications and Public Relations, have become invaluable resources.

Literature Cited
1. Higgins, A., Bird lovers see roaming cats as a major threat to many species, in The Washington Post. 2010: Washington, DC. http://www.washingtonpost.com/wp-dyn/content/article/2010/09/28/AR2010092803999.html

2. Seife, C., Proofiness: The Dark Arts of Mathematical Deception. 2010: Viking Adult.

3. 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.

4. Winter, L., “Popoki and Hawai’i’s Native Birds.” ‘Elepaio: Journal of the Hawaii Audubon Society. 2003. 63(6).

5. Hatley, P.J., Feral Cat Colonies in Florida: The Fur and the Feathers Are Flying. 2003, University of Florida Conservation Clinic: Gainsville, FL.

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.

The Scat Hits the Fan

Relative to other studies of the domestic cat’s predatory habits, Carol Fiore’s 2000 thesis work is cited only occasionally in the literature. [1, 2] Indeed, it might easily go unnoticed were it not for its inclusion in the American Bird Conservancy’s brochure Domestic Cat Predation on Birds and Other Wildlife, and the fact that Fiore posted a summary of the study on her website—making much of its content available to anybody interested in the topic.

Fiore’s “primary goal,” she writes, “was to estimate the number of cats in Wichita, the average number of birds killed per cat and the total number of birds killed by cats each year.” [3] In fact, there was more to it than that.

Fiore was also trying to quantify the number of birds killed by cats without their owners’ knowledge, thereby addressing a concern frequently expressed by researchers whose predation estimates rely on prey records kept by cat owners. [4–7] In other words, how many birds were being killed by cats, really?

Fiore’s thesis project was an ambitious undertaking—perhaps too ambitious. Although her goal was admirable, her small sample size, flawed analytical methods, and various confounding factors cast considerable doubt over her findings. In addition, Fiore’s thesis document is peppered with evidence of bias. Indeed, she raises questions about her motivation for the project (and underlying assumptions) when, early on, she refers uncritically to the ABC’s Cats Indoors! campaign and the Wisconsin Study, and mischaracterizes the work of William George (see Note 1).

I’m afraid that, in the end, Fiore’s work does little to enhance our understanding of the domestic cat’s hunting behavior. In fact, because her conclusions tend to misrepresent the study’s findings, Fiore actually does more to perpetuate the mythology surrounding predation than the science.

The Study
Fiore’s research incorporated several methods, each intended to provide a key piece of the predation puzzle:

  1. Twenty-eight Wichita, Kansas cat owners were recruited and asked to record the number and, when possible, also the species, of birds killed by their 41 cats over the period of approximately one year.
  2. Some of these same participants were asked to collect scat samples, which were then analyzed for feathers. Detection of feathers was used to account for kills not reported by cat owners.
  3. The behavior of eight participating cats was observed with the help of radio collars.
  4. Cat density in the area was estimated by combining telephone survey results (regarding the proportion of area cats that received the rabies vaccine) with information from local veterinarians (regarding the yearly total of rabies vaccines administered to cats).
  5. Using Christmas Bird Count data, the density of Northern Cardinals in the Wichita area was estimated.
  6. The impact of free-roaming cats on the population of cardinals was then estimated by combining findings from each of the investigations described above (with the exception of the radio collar monitoring).
  7. A second telephone survey was conducted, this time to learn about residents’ attitudes concerning possible cat regulations (e.g., leash laws, licensing, etc.).

Birds Brought Home by Cats
Twenty-nine (71%) of the cats were reported to have killed birds during the study period, while 12 (29%) were credited with no kills. (These figures would later be adjusted based on the results of the scat analysis, as described below.) However, multi-cat households posed a particular problem. “For owners with more than one cat,” writes Fiore, “kills were alternated between cats if the owner was unsure of the cat responsible.” [3]

As a result of her “alternating attribution” (my term, not Fiore’s) method, it’s possible that five cats were incorrectly included among the hunters (see Note 2 for details). If so, the proportion of hunters was not 71%, but 61%.

Other Studies
Either way, Fiore’s findings correspond reasonably well with those of a five-month survey of 618 British households, in which 986 cats brought home 14,370 prey items. This research revealed that, although 91% of cats returned at least one item, “approximately 20–30% of cats brought home either no birds or no mammals.” [5] Her results also seem to be in line with those published by Churcher and Lawton, whose yearlong “English Village” study (involving approximately 70 cats and 1,090 documented prey items) found that that 8.6% of cats brought home no prey [4] (though the authors don’t specify the percentage of cats that returned no birds).

On the other hand, it is not uncommon for such studies to find that more than half of the study cats returned no prey. In their pilot study of cat predation in Bristol (UK), for example, Baker et al. reported that 77 cats returned a total of 212 prey items to 52 participating households, but that “in each sampling period, the majority of cats (51–74%) failed to return any prey.” [6] Their subsequent 12-month study (this time involving 186 Bristol households, 275 cats, and 495 prey items) found a similar level of apparent non-hunters: roughly 61%. [7]

Any number of factors might contribute to these apparent differences, perhaps the most likely “culprits” being environmental (e.g., density of both birds and cats, habitat type and size, etc.) and sampling bias (as Baker et al. put it, “cat owners whose pets were killing lots of birds may have wished to hide the fact; alternatively, they may have been keen to show off their cat’s prowess.” [7])

Add It Up
Fiore began to quantify predation by calculating, based on the number of birds brought home by study cats, an average number of birds killed each year per cat. But, as I’ve discussed previously, using the average to describe predation rates (the distribution of which is highly skewed) overestimates the impact of cats on wildlife. Barratt offers a useful rule-of-thumb method (one echoed by Fitzgerald and Turner [8]) as an alternative:

“…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.” [9]

Using the median—1.91 birds/cat/year—instead of the mean, cuts Fiore’s estimated predation rate of 3.44 nearly in half. (Among the more puzzling items I uncovered while reviewing Fiore’s thesis was her apparent miscalculation of the average predation rate—where Fiore comes up with 3.44 birds/cat/year, I get only 2.79. See Note 3 for a detailed explanation.)

In any case, what’s far more interesting is how Fiore adjusts her estimate based on the results of feathers discovered in scat.

Scat Analysis
Three of Fiore’s participants (who, together, owned six of the study cats) collected and bagged their cats’ scat for five consecutive days on a monthly basis. A fourth owner participated in this part of the study for just one month, and collected scat for three days.

Additional scat data was acquired via “litter box cleanups,” in which “a few volunteers were convinced to bag the entire contents of the litter box when it was cleaned.” [3] The results, according to Fiore, were rather dramatic:

“Out of 215 separate scat analyses, each of which could have composed several beakers of fecal material, feathers were found a total of 28 times. In only one instance, however, did the owner know that a bird had been killed and/or consumed.” [10]

Equally dramatic were the mathematical and statistical gymnastics Fiore employed to arrive at her conclusions. Her figure of 21%, for example, as “a mean value of the percentage of time a cat could be expected to ingest a bird with no owner knowledge,” [10] remains a mystery to me. Despite numerous attempts, I have been unable to sort out exactly how Fiore arrived at this figure.

Dividing 27 occurrences of “unexpected” feathers by 214 total analyses (subtracting in each case for the one instance of “expected” feathers) ought to get us close, it seems—but falls well short (12.6%).

Litter Box Cleanups
Of the 215 analyses, 24 were litter box cleanups, a data collection method plagued with problems. To begin with, only 11 owners (representing 19 cats) participated. Fiore acknowledges the limitations associated with this small sample size, but overlooks a thornier issue.

Fiore considered each cleanup—regardless of how many cats were using the litter box, or for how many days—a single data sample. If a feather was found during analysis (the details of which are described on Fiore’s website), then one additional kill was attributed to a single cat (again, alternating among cats in multi-cat households). While this is a conservative approach in one respect—no more than one bird could be recorded for any positive result—it fails to adequately account for the high number of negative results. A litter box containing the waste of three cats, accumulated over a period of five or more days (six of the 24 cleanups were of this type, and in only one case were feathers found), was treated no differently from one containing a single day’s waste from one cat.

This per-household approach allows a negative result in the first case to be offset by a positive result in the second—despite their very different implications.

On the other hand, at least two volunteers involved in the litter box cleanups also owned indoor cats, and it was impossible to determine whether it was their indoor or indoor/outdoor cats that were “contributing” to the study. This may have resulted in some false negatives.

Given all the uncertainty involved with Fiore’s litter box cleanups, it’s difficult to see how this aspect of her study contributes in any meaningful way to the overall findings. Better, I would say, not to include these results in any calculations—and perhaps disregard them entirely.

Monthly Collections
Fiore’s primary method (making up 191 of the 215 analyses) for scat analysis proved less problematic than the litter box cleanups—but was not without its own shortcomings.

Again, the sample size was quite small—only four participants in all (representing seven cats). And, once again, owners of multiple cats (two of the three long-term participants) were treated—from a statistical point of view—as if they each owned just one cat. A negative result in a three-cat household was weighted the same as an instance of feathers found in a single-cat household.

Worse, by alternating attributions of kills that could not linked to a specific cat in a multi-cat household, Fiore effectively makes hunters out of non-hunters (see Note 2 for a detailed explanation). In fact, given enough of these attributions—and it wouldn’t take many—all of the study cats would be categorized as killers.

Taking into account the number of cats in each household that participated in monthly collections (see Note 4), the number of scat analyses rises dramatically, from 215 to 354—and the average occurrence of feathers drops to just 7.6%.

Lucky 13
In the case of Cat 13—the study cat with the most “scat kills” (instances of feathers detected in scat when no birds were returned home) by far—feathers were found in 14 of 80 (17.5%) daily samples collected, prompting this reaction from Fiore:

“It is interesting to speculate as to the outcome of this study if all the volunteer owners had been as conscientious as this particular owner in collecting scat every month. Additionally this owner, who is retired, is very mindful of her cat’s whereabouts but still failed to find many kills.” [3]

But even Cat 13’s apparent penchant for secretive hunting yielded a frequency of found feathers well below Fiore’s suggested overall rate of 21%. And what about the other two long-term participants, whose 23 monthly samples (108 days’ worth—collected from five cats, not one, don’t forget) revealed just eight occurrences of feathers? Their frequency of secretive hunting was 7.4%—before accounting for the multiple cats involved (as described in Note 4), which would drop the rate to just 3%.

Was the owner of Cat 13 any more conscientious than the other two? Perhaps. Fiore notes that this woman, “appeared to be very serious about the study and never failed to turn in scat on a monthly basis; reminders were never required.” [3] Still, the other owners were hardly sitting on the sidelines—they turned in 108 samples between them. And it’s not clear what detrimental effect requiring a reminder might have had on the results; on the contrary, Fiore writes: “It is believed that scat volunteers conducted their collection correctly.” [3]

It’s difficult not to detect bias in Fiore’s praise for the diligence demonstrated by Cat 13’s owner—or, more to the point, her appreciation for the cat’s performance. Although this cat’s behavior is—as illustrated by Fiore’s own data—exceptional, Fiore seems to suggest that it’s the norm.

Corroboration and Disclaimers
Fiore is quick to point out various factors that would have allowed kills to go undetected by scat analysis. The condition of the birds recovered, for example, suggests that some cats don’t eat their prey, in which case scat would not have contained feathers. Nestlings, because they lack feathers, also would go undetected.

And even adult birds, suggests Fiore, may not have feathers to be discovered later. “Generally,” she writes, “cats pluck the feathers before consuming the bird.” [3] Although Fiore cites the work of other researchers on this point (work I’ve yet to chase down), her own findings seem to contradict this claim; plenty of feathers were found in scat. (Fiore’s claim also begs the question: If cats are expected to strip the feathers from the birds they kill, why use feathers found in scat as a measure of predation?)

Fiore is doubtful that “one of the study cats ate a bird it did not kill and that in turn feathers were detected in the scat,” [3] but Fitzgerald and Turner have suggested otherwise:

“Carrion is eaten, but is difficult to distinguish from animals killed by cats, unless it is from a large animal that a cat could not kill (e.g., sheep or kangaroo). Even the presence of maggots with the food is not a certain indicator, because cats may return later to prey they have killed and cached.” [8]

Although Fiore acknowledges the challenges inherent in her analysis method, she argues that they are outweighed by the benefits:

“Scat analysis is probably the most reliable estimate of bird kills, although it is a very conservative one. The results are hard to refute. When a feather is found it is proof that a kill was made or a carcass consumed… scat analysis is important because often cats do not bring their kills to the owner, and frequently the owner is not home to accept a kill should one be presented. Many of the owner volunteers reported not seeing their cat(s) for many days in a row (one owner did not see her cat for several months during the study). Collected kills were very conservative, and seemed to be based in part on the relationship of the owner with their cat(s). Unfortunately, absentee owners were the ones most unwilling to provide scat.” [3]

It seems Fiore wants to have it both ways: When it comes to defending the value of scat analysis, she’s quick to point out how much predatory activity the owners might be missing. When she’s emphasizing the conservative nature of prey tallies, though, Fiore cites a number of detailed firsthand accounts from cat owners—painting a rather different picture of owner involvement:

  • “There were numerous calls during the course of data collection about missing remains, cats seen eating birds but no remains could be found, cat running off with prey…”
  • “The wife of one of the volunteers admitted to seeing her cat drag a cardinal under the porch, but she would not retrieve it…”
  • “The owner of Cat 30 reported that she had seen… her cat eat an entire bird (even the head) and that there was no evidence left to give us.”

Her inconsistency raises questions not only about her findings, but also—far more unsettling ones—about her objectivity as a researcher.

Found Feathers
Despite results that are—at best—mixed, Fiore’s conclusions are imbued with certainty and drama. They also tend to misrepresent her research. Fiore’s claim that “scat analysis may indicate, as in this study, that a far greater number of birds are consumed than was previously thought” [3] is based on her misuse of means to characterize predation levels. Using medians instead, it becomes clear that—in terms of the distributions’ central tendency—there is no difference between her original data set and the one that includes scat kills.

More problematic, though, are Fiore’s claims about the secretive hunting habits of cats:

“Probably the most important information which can be gained from the scat analysis (coupled with owner bird collection) is that most cats do kill birds. And in all cases but one, when feathers were found in scat, the owner was unaware that the cat had eaten a bird. This and other data from this study would seem to refute Dr. Patronek’s claim that ‘cats tend to bring prey home.’” [3] (See Note 5 for details regarding Fiore’s apparent dispute with Patronek.)

Actually, Fiore’s own data indicate that cats do, in fact, “tend to bring prey home”—nearly four in five, if her mysterious 21% figure is to be believed. And her assertion about the surprising nature of kills revealed through scat analysis is—although technically true—highly misleading. She seems to be suggesting that scat collection was done randomly, in which case we would expect some collections to correspond with documented kills. Fiore’s reporting, however, indicates no such randomness. In fact, it’s entirely likely that participants (thinking such activity would at least be redundant, or worse, detrimental to the study) would have collected scat only when they were unaware of their cat(s) having killed a bird.

By framing her findings this way, Fiore effectively dismisses the vast majority of analyses (187 of 215, or 87%, using her analysis method; 326 of 354, or 92%, accounting for multi-cat households) in which no feathers were found.

When the ABC summarizes Fiore’s work in their brochure Domestic Cat Predation on Birds and Other Wildlife, they only make matters worse by conflating different aspects of her research:

“In a study of cat predation in an urban area, 83% of the 41 study cats killed birds. In all but one case, when feathers were found in scat, the owner was unaware that their cat had ingested a bird. In fact, the majority of cat owners reported their cats did not bring prey to them. Instead, the owners observed the cats with the bird or found remains in the house or in other locations.” [11]

Reading the ABC’s version, one might easily get the impression that all 41 cats were involved in the scat analysis, or that the scat collections were done randomly. (Or that cats, in order to be considered cooperative participants in predation studies, are expected to deposit their prey in the laps of their owners, or some other pre-determined location.)

Connecting the Dots
Let’s set aside my (numerous) complaints regarding Fiore’s scat analysis, and my claim that she both miscalculated and misused the average predation rate. Assuming both figures are valid, Fiore’s use of that 21% figure to adjust the predation rate upward, from 3.44 to 4.2 birds/cat/year is also a problem. The scat analysis should (again, assuming it was done properly, included sufficient sample sizes, etc.) reveal something about the secretive hunting behavior of the study cats—in terms of (1) its frequency, and (2) its extent. Fiore’s misstep is in linking the frequency directly to predation levels.

Properly adjusting the estimated predation level would involve, first, correcting the proportion of cats that hunt to account for the frequency of secretive hunters. Using Fiore’s data to illustrate:

71% + [(100%-71%) x 21%] = 77%

Once we adjust for those cats that don’t bring prey home, we can multiply this figure by the number of outdoor cats (see Note 6). Again, using Fiore’s data (described in the Cat Density section below):

40,836 pet cats x 43% allowed outdoors = 17,559 hunting cats

Multiplying this result by the median predation rate (1.91), we get a total of 33,538 birds/year killed by pet cats in Wichita—less than half Fiore’s estimate of 73,750. (This figure might be refined further by considering separate predation levels: one for the secretive hunters, and another for those cats known to bring prey home. Unfortunately, Fiore’s sample size is too small to make such a comparison, but it’s not difficult to imagine different hunting behaviors resulting in different success rates.)

To reiterate, I’m using Fiore’s numbers here only to illustrate how I would connect the dots between scat analysis results and predation levels.

Two Key Points
Fiore’s goal of obtaining a more accurate tally of birds killed by cats was (and is) admirable. However, her use of scat analysis was largely unsuccessful in achieving that goal. In fact, Fiore’s analysis method actually added to the uncertainty in two important ways:

  1. By alternating attributions of kills that can’t be linked to any one cat in a multi-cat household, Fiore essentially categorizes each one of them as a hunter.
  2. By weighting multi-cat households no differently from single-cat households, Fiore ignores a great deal of evidence suggesting that most cats are not, in fact, hunting without their owners’ knowledge. Although the number of “scat kills” is conservative as a result, her analysis method gives greater importance to what is unknown than to what is known.

Radio Tracking
Among the many challenges Fiore ran into while trying to track study cats were owner objections, physical barriers (e.g., fences), and radio signal strength/continuity in an urban setting. As a result, she was able to study only eight cats for a total of 57 hours (almost all during daylight hours).

Given the limited value of Fiore’s tracking activities—and my focus on the aspects of her thesis that pertain more directly to predation—I’ll move on to her estimate for the number of cats in Wichita.

Cat Density
Fiore used two different methods to estimate the number of cats in Wichita. The first, which is rather clever, involved combining the results of two telephone surveys: the Pet Ownership Survey was used to (among other things) poll respondents about whether or not they had vaccinated their cat(s) against rabies; a survey of local veterinarians was used to estimate the annual total of such vaccinations in Wichita. “If 500 cats received vaccinations,” writes Fiore, “and respondents indicated that 50% of pet cats had been vaccinated, 1000 cats would be the expected density.” [10]

For the second method, Fiore multiplied the number of Wichita households by the estimated number of cats per household (1.52), as determined through a random telephone survey.

Results of the first method yielded an estimate of 35,737 pet cats in Wichita, whereas the second method produced an estimate of 40,836 pet cats. (The skewed nature of the cats/household distribution (many owners having one or two cats, and a few having many cats) will tend to push such estimates upward.)

In addition, Fiore estimates (in her original thesis document, but not in the summarized version that appears on her website) the number of stray and feral cats in the city, ultimately arriving at a figure of 124,537. Deriving such estimates is always dodgy work, as so little trustworthy information is available. Additional caution is in order when these figures are used to project predation levels of stray and feral cats, as Fiore has done (as described in the Christmas Bird Count section, below).

For one thing, there are some questionable assumptions wrapped up in her estimates—not the least of which is that the predation rates and patterns of stray and feral cats are similar to those of pet cats. Clifton has suggested that they are not:

“The feral cat toll on birds is unlikely to be more than half as high as the pet cat toll. First, there may be twice as many free-roaming pet cats as ferals old enough to hunt for a living. Second, ferals who hunt for a living tend to hunt mice by night, not birds, who are mostly not out at night. Third, feral cats appear to hunt no more, and perhaps less, than free-roaming pet cats. This is because, like other wild predators, they hunt not for sport but for food, and hunting more prey than they can eat is a pointless waste of energy… Finally, relatively few cats are even capable of successfully hunting birds.” [2]

Christmas Bird Count
Fiore used data from the Wichita Audubon Society’s “first area-wide bird count of Northern Cardinals,” [3] an event coinciding with the National Audubon Society’s 99th annual Christmas Bird Count. Combining this data with the number of households in the city, she estimated that there were 316,477–424,922 cardinals in Wichita at the time.

It’s important to remember, as is made clear on the North American Breeding Bird Survey website, that such surveys provide “an index of relative abundance, rather than a complete count of breeding bird populations.” Fiore admits, “a census of a single bird species effected [sic] by urban cats in Wichita is an estimate of population density within an accuracy of one order of magnitude,” [3] but persisted.

As a result, Fiore was able to compare estimates of the overall cardinal population with estimates of those killed by cats. However, her “accounting practices” suggest that she’s not exactly impartial on the subject of predation. Fiore states unequivocally, for example, “the mean of 2.98… cardinals seen per residence is high as very few surveys were returned by people who saw no cardinals.” [3] Sure that “people only reported when they saw cardinals, thus skewing the data towards high values,” Fiore discards the mean and uses frequency quantiles instead.

Among the possible sources of participant bias Fiore cites:

“…adding counts together rather than reporting total numbers seen at one time, counting birds on someone else’s property, estimating numbers by song alone, or sending in the forms with numbers that did not exist on December 19 but that the resident had seen on some previous occasion.” [3]

Perhaps she was correct in her assessment, but it’s peculiar that Fiore never expressed a similar concern for her obviously skewed distribution of birds killed by cats—and as a result, overestimated predation levels. In short, she seems determined to lower the estimate of birds in the area while at the same time raising the estimate of birds thought to be killed by Wichita’s cats. (In fact, her thesis is littered with such maneuvering; Fiore uses nearly every instance of uncertainty to imply an impact on wildlife greater than her research actually suggests.)

Fiore’s bird collection data indicated that 7% of the birds taken were Northern Cardinals. Combining this figure with her estimates of the populations of all outdoor cats and cardinals in Wichita, she concludes, “there are at least 43,035–50,285 Northern Cardinal deaths per year due to cat predation.” [3] This corresponds to roughly 15% of her estimated cardinal population—a figure Fiore describes as “extremely conservative.”

Impact of Free-roaming Cats
Considering the numerous limitations of her study (many of which she acknowledges), Fiore seems quite comfortable extrapolating her results—arguing, for example, that “over half a million birds meet their death each year in the city of Wichita because of a cat.” [3] Of course, this figure relies on dubious estimates of the number of outdoor cats, an exaggerated predation estimate, and other factors that cast serious doubt on its accuracy.

Fiore’s confidence may come, in part, from the fact that other researchers have reported similar findings. But, as I have gone to great lengths to emphasize over the past few months, such findings rarely hold up to careful scrutiny. And sometimes, results are simply misunderstood—as when Fiore misinterprets Fitzgerald’s work:

“…several studies have been done to access [sic] the importance of birds as a percentage of total diet, as in Fitzgerald [12] who estimates birds represented 21% of cat diets.” [3]

In fact, Fitzgerald was referring not to the percentage of dietary intake, but of how often birds were found in scat or stomach contents (a distinction I explain in detail here):

“On all continents, birds are usually much less important than mammals; birds were present on average at 21 per cent frequency of occurrence, and mammals at 68 per cent. Many species are represented by just one or two individuals.” [12]

Something else Fiore overlooks is that the type of predation observed by her participants may have been largely compensatory; that is, the birds killed were of sufficiently poor health that they were unlikely to survive anyhow. Two studies have reported such findings. [7, 13] If this were the case, even her inflated estimates—however dramatic sounding—would actually have little impact on the population of Wichita’s birds.

In any case, the cardinals in the area seem to be doing fine. Between 1970 and 2000, Wichita’s human population increased 24.5%, from 276,554 to 344,284. Such an increase—accompanied by various related development activities—is generally associated with habitat loss, fragmentation, pollution, and any number of other factors that adversely affect bird populations. Including more cats. Nevertheless, data from the North American Breeding Bird Survey suggests that the number of Northern Cardinals in the area was on the increase over this period.

Wichita Cardinals Over Time
Caption: BBS Data: Northern Cardinals for Three Wichita-area Survey Routes (adapted from North American Breeding Bird Survey website)

Cat Regulations
Fiore used a telephone survey of Wichita residents to inquire about a range of pet ownership issues, as well attitudes concerning possible regulations affecting cats/cat owners. Among the questions Fiore posed to Wichita pet owners:

“At the present time dogs have to be licensed and kept on leashes. How do you feel about having cats regulated so that they would have to be licensed and confined to the owner’s property?”

Thirty-one percent of cat owners were completely opposed, while 44% said they were at least somewhat in favor—“a surprisingly high figure,” as Fiore notes. Pet owners were then asked a follow-up question:

“If it were found that unregulated cats are killing too much wildlife, would you change your opinion?”

Survey results are always tricky to interpret, and two people can often draw very different conclusions from them. Rather than focus on the responses, then, I’d like to take just a moment to focus on the question—starting with the term unregulated. Is that even necessary? How about simply cats? And what do me mean by wildlife here? And how much is too much?

Nearly half of respondents said that they would not change their minds, and Fiore sounds downright exasperated with their explanations:

“Cat owners are in denial about what their cats are doing. They seem sad over the death of a cardinal, but they refuse to take responsibility for the cat by stating ‘There is nothing I can do’ or ‘…but that’s what cats do.’ The owner of study cat 14 wrote ‘Cats are part of nature same as birds. Species come and go. I don’t think nature should be artificially regulated.’” [3]

Fiore clearly disagrees. Indeed, she tipped her hand much earlier, when, in Chapter 1, she wrote:

“If a human killed any of these birds or was caught in possession of them without a valid permit, he or she would face penalties including fines, and depending on the severity and species, possible jail time. Cats across America and their owners face no punishment.”

*     *     *

A story in the April 18, 1998 edition of The Wichita Eagle explained Fiore’s proposed project this way:

“Fiore, a graduate student at Wichita State University, will spend a year counting Wichita cats and their feathered victims for her master’s thesis. As bird populations decline, Fiore thinks it’s important to know how far cats are sinking their teeth into the feathered world… She points out that even the cutest kitty can be a remarkable hunter, although skill varies from cat to cat. But Fiore doesn’t want people to think she’s anti-cat. ‘I’m out to study the problem.’” [14]

In the same piece, Fiore brings up the Wisconsin Study (referring to its “intermediate value” of 39 million birds), and it’s revealed that she’s the vice president of the Wichita Audubon Society. Nevertheless, Fiore assures readers of her objectivity: “We’re just scientists who want to see if there’s a problem.”

Fiore’s thesis dedication, too, suggests an air of integrity and goodwill:

“This thesis is dedicated to my cat owner volunteers who made this study possible and to cat lovers and bird lovers around the world in the hopes that we can all work together to preserve native wildlife.” [3]

Having spent weeks reviewing Fiore’s work, though, I’m not buying it. In fact, I can’t help but read in her dedication an inside joke of sorts: her invitation is to preserve native wildlife; domestic cats, as she makes clear elsewhere, are not native.

In a follow-up story for The Wichita Eagle, Fiore reported her results: Wichita cats kill anywhere from 542,000 to 645,000 each year. But, according to the Eagle’s Roy Wenzl, it wasn’t the results that got some residents worked up. “Fiore’s study upset people. Not what she found. But what she did, in raising the question.” [15]

“‘I didn’t understand that,’ said Bob Gress, a cat owner, a naturalist and the director of the Great Plains Nature Center, who helped her with her study. ‘All she was doing was collecting information. I don’t think any of us should ever be afraid of the truth,’ Gress said. ‘But some people saw this as an assault on cats. Even some veterinarians seemed to resent what she was doing.’” [15]

Gress’ comment got me thinking not just about Fiore’s thesis, but also about how it’s been used—primarily by the ABC. As much as we might like to believe otherwise, scientific inquiry doesn’t happen in a vacuum; there is always a context to consider. It’s clear from her document that Fiore was well aware of the debate surrounding free-roaming cats at the time—and must have a good idea, too, of the possible implications of her work (e.g., ammunition for those who oppose free-roaming cats and TNR, the possible wholesale extermination of stray and feral cats, etc.).

And then there’s the matter of just how much truth there is in Fiore’s findings—plagued as they are by her flawed analysis and obvious bias.

Which is not to say that she (or anybody else) should be discouraged from studying such complex, controversial issues. But there is a great responsibility that comes with such endeavors. Fiore, in her thesis work, simply didn’t live up to that responsibility.

Notes
1. Fiore writes: “A researcher in southern Illinois estimated that his three house cats, which he followed for 6 years, only brought home about 50% of killed prey.” [16] As I’ve pointed out previously, this is a surprisingly common misunderstanding of George’s work. In fact, George was merely adjusting predation levels based on the fact that the “delivery area” was not always monitored: “…the study registered 50 percent of the cats’ captures—a percentage roughly corresponding to: 1, the average amount of total time the delivery area was under observation for recording prey; and 2, the number of prey items logged in the same year when the delivery area was under continuous day-and-night scrutiny, compared to the number logged (during equivalent seasonal and hourly periods) when continuously scrutinized for lesser amounts of time.” [16]

2. Fiore provides little detail regarding the application of her alternating attribution method, requiring some speculation on my part. An example, however, may prove illustrative. Consider Cats 17 and 18, which lived in the same home. During the bird collection phase of the study, Cat 17 was credited with just two kills. Cat 18, on the other hand, brought home 17 birds—clearly the more successful hunter. The question is: Did Cat 17 really kill those two birds, or are these simply the result of kills that could not be attributed to either cat?

At any time during the yearlong study, kills that could not be connected directly to a particular cat were, as Fiore explains, “alternated between cats.” Imagine if, at the time Cat 17 had 15 known kills, another kill was discovered—but this time, it was unclear which cat was responsible. That kill, then, would be attributed to Cat 17, bringing its total to 16. The next such kill would be attributed to Cat 18—effectively shifting its status from non-hunter to hunter. Two more such instances would yield the results described by Fiore: two kills for Cat 17 and 17 for Cat 18—though it should be clear that just two “mystery kills” would, using Fiore’s analysis method, create the impression that both cats are hunters. (In fact, were it not for their random numbering—Cat 17 being credited with the first “mystery kill” only because of its lower ID number—such an impression would result from just one such kill.)

To be clear: the scenario described above is speculative. But, given the impact of Fiore’s alternating attributions—increasing rather dramatically the proportion of apparent hunters—careful scrutiny is warranted.

3. Calculating the mean should be quite straightforward, of course. Fiore first calculated a daily rate for each cat by dividing that cat’s catch by the number of days in which its owner participated in the study. She then averages that rate over all 41 cats (coming up with 0.0094, compare to my 0.0076), and multiplies the result by 365 days/year.

4. Using this analysis method, a five-day collection from a three-cat household would constitute not five, but 15 analyses. Now, there’s no way of knowing that all three cats contributed to the scat collection; conversely, there’s no reason to think that just one cat contributed, as Fiore assumes.

5. At times, Fiore’s thesis reads as if it was a rebuttal to Gary Patronek’s article, Free-roaming and feral cats—their impact on wildlife and human beings, which was published around the time Fiore was conducting her research. Interestingly, had Fiore read Patronek’s paper more closely, she might not have used the mean to estimate predation rates. “The small proportion of cats with a large number of kills,” writes Patronek, “indicate that the number of animals killed per cat has a skewed distribution, which would tend to bias the mean upward.” [17]

6. Fiore is skeptical of her Pet Ownership Survey results, which indicate that 43% of cat owners keep their cats indoors (“People who interpreted this question to mean that because the cat was inside ‘most of the time’ it was an indoor cat, would be incorrect for purposes of this study.” [10]). However, as Merritt Clifton points out, it’s likely that she actually overestimates the number of outdoor cats when she “decided, based on a survey of Wichita residents, that about half of all cat-keepers allow their cats to roam, and presumed that could be extrapolated to mean that half of all pet cats roam.” This, writes Clifton, contradicts Animal People findings “that cat-keepers whose cats do not roam have, on average, from two to three times more cats than those whose cats can roam.”  [2] Further support comes from a 2003 survey that found 60% of cats were kept strictly indoors, and nearly half of those allowed outdoors were out for less than two hours each day. [18]

Literature Cited
1. Dauphiné, N. and Cooper, R.J., Impacts of Free-ranging Domestic Cats (Felis catus) on birds in the United States: A review of recent research with conservation and management recommendations, in Fourth International Partners in Flight Conference: Tundra to Tropics. 2009. p. 205–219.

2. Clifton, M. Where cats belong—and where they don’t. Animal People 2003 [cited 2009 December 24].  http://www.animalpeoplenews.org/03/6/wherecatsBelong6.03.html.

3. Fiore, C.A., The Ecological Implications of Urban Domestic Cat (Felis catus) Predation on Birds In the City of Wichita, Kansas, in College of Liberal Arts and Sciences. 2000, Wichita State University: Wichita, Kansas

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

5. Woods, M., McDonald, R.A., and Harris, S., “Predation of wildlife by domestic cats Felis catus in Great Britain.” Mammal Review. 2003. 33(2): p. 174-188.

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.

7. 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.

8. 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.

9. 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.

10. Fiore, C.A. and Sullivan, K.B. (2000) Domestic Cats (Felis catus) Predation of Birds in an Urban Environmenthttp://www.carolfiore.com/Article.html Accessed July 27, 2010.

11. 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

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

14. Potter, T., Counting Cats and Their Winged Prey, in Wichita Eagle, The (KS). 1998. p. 9A

15. Wenzl, R., Are You Harboring a Killer on Your Couch?, in Wichita Eagle, The (KS). 1999. p. 9A

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

17. 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.

18. 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.