Cats kill 2.4 billion birds and 12 billion mammals every year in US alone

[mcb]

In Animals in Transition, Temple Grandin claims that the cats hunt and kill instinctively but must be taught what to do after that. I think that the unowned cats, however, have to work out some of the details anyway, or starve.

I have seen ecological problems involving cats described in documentaries; that's my only contact with it apart from my own cats, one of whom (a stray that my mother took in) would in his early days hunt mice, kill them, and bring what was left to us.

 

[treesparrow]

By domestic cats I meant well looked after owned ones and not individuals once domesticated but now gone feral for whatever reason. I agree it is feral ones causing the bulk of the killing and I again I'm not suggesting belling those or any taking any other measures, which might hamper their abilities to kill and feed themselves. I don't know what can be done about this problem, that is, if it is a problem. Is the level of cat predation really having a long term effect on bird population levels ? (that maybe is the most important question). Would those creatures killed by cat succumbed to some other predator anyway - had the cats been absent - partly because they were young, sick or inexperienced? Who knows?

Domesticated cats are one of the few species that will kill another animal just for the exercise, and not for food. That is why they are so devastating when the population goes too high in the wild. In our area, stray cats, and barn cats are killed by cars and coyotes more than they die from starvation.

Where I live in the country, the local song bird population dips as the stray cat population rises. Its evened out by coyote packs, which prey on strays of all species.

Having seen how cats can destroy an ecosystem, I'm not averse to culling any population of stray cats when an endangered ecosystem is being stressed by them.

On the other hand these just seem to be personal, anecdotal local observations. Which may be valid or perhaps not. :) Bird population can decline for a variety of reasons, pollution, food shortages, natural climate change,etc. Maybe what's really needed is data from long term studies from wide geographical areas - both urban and rural. This essay critiquing other studies on the numbers estimated for wild bird and animal deaths put down to cat predation, illustrate just how complex the situation is, osit.

A Critical Assessment of “Critical Assessment”—Part 1

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

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

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

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

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

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

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

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

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

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

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

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

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

Works cited in “Critical Assessment” excerpt:

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

_http://www.voxfelina.com/2010/05/a-critical-assessment-of-%E2%80%9Ccritical-assessment-part-1/

Part 2

A Critical Assessment of “Critical Assessment”—Part 2

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

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

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

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

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

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

* * *

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

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

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

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

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

* * *

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

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

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

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

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

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

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

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

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

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

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

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

http://www.voxfelina.com/2010/05/a-critical-assessment-of-critical-assessment-part-2/

Edit - for highlighting.

 

[Ben]

Reminds me of the story of the Stephen's island wren

-http://en.wikipedia.org/wiki/Stephens_Island_Wren

Illustrates just how efficient our little feline companions can be.