An Eastern Phoebe with a mangled wing awaits death at the jaws of a pet cat.
The National Geographic Society and University of Georgia recently teamed up to apply “critter-cam” technology to understanding the lives of pet cats, documenting not only their predatory habits but the many hazards they face.
The team, led by Kerrie Anne Loyd of the University of Georgia, attached small video cameras to 60 outdoor house cats in the city of Athens, Georgia. The cats’ owners were recruited through newspaper ads and assisted the team by doing daily downloads of video from the cameras.
The most important findings were about cat predation. Loyd said:
In Athens-Clarke County, we found that about 30 percent of the sampled cats were successful in capturing and killing prey, and that those cats averaged about one kill for every 17 hours outdoors or 2.1 kills per week. It was also surprising to learn that cats only brought 23 percent of their kills back to a residence. We found that house cats will kill a wide variety of animals, including: lizards, voles, chipmunks, birds, frogs, and small snakes.
It’s no wonder so many cat owners are unaware that their pets ever kill wildlife. Even if they found every animal their cats brought home, they’d still miss more than three quarters of the death toll.
The cats in the study were outside for only 5 to 6 hours a day on average. It’s sobering to compare these well-fed pets to homeless/feral cats that are outdoors 24/7/365 and may hunt for survival as well as recreation.
Dr. George Fenwick, President of American Bird Conservancy, found the project’s findings alarming:
If we extrapolate the results of this study across the country and include feral cats, we find that cats are likely killing more than 4 billion animals per year, including at least 500 million birds. Cat predation is one of the reasons why one in three American bird species are in decline.
Think about that: 4 billion animals, including at least a half billion birds, that die purely because of human irresponsibility.
The cameras also documented risky behavior that should alarm cat lovers: crossing roads, hiding under vehicles, climbing trees, exploring roofs and storm drains, confronting dogs, opossums, and other cats, and killing small mammals that are vectors for diseases such as toxoplasmosis and Lyme disease.
The National Geographic & University of Georgia Kitty Cams Project
American Bird Conservancy: “KittyCam” Reveals High Levels of Wildlife Being Killed by Outdoor Cats
Life, Birds, and Everything 
It’s curious that when University of Georgia researcher Kerrie Anne Loyd spoke with CBS Atlanta in April (http://www.cbsatlanta.com/story/17711012/kitty-cameras-show-athens-cats-on-the-prowl), though, she conceded: “Cats aren’t as bad as biologists thought” (Paluska, 2012). What’s changed? My guess is she realized that such comments are liable to limit future career opportunities.
A few comments on the news release:
“Of particular interest,” notes ABC and TWS, “bird kills constituted about 13 percent of the total wildlife kills.” Thirteen percent of how many? As the Athens Banner-Herald reported in April (http://onlineathens.com/local-news/2012-04-24/kitty-cams-show-what-athens-roaming-cats-are), “just five of the cats’ 39 successful hunts involved birds” (Shearer, 2012). That’s right: five. Fifty-five cats, 2,000 hours of video—and just five birds. Not so impressive when it’s put in context, is it?
And which species of birds are we talking about? Are these common? Rare? Native? Non-native? Etc. It’s curious that ABC and TWS, which claim to be concerned with the “ongoing slaughter of wildlife,” aren’t troubled by such “details.” Interestingly, the only avian casualty documented on The National Geographic and University of Georgia Kitty Cams Project website (http://www.kittycams.uga.edu/photovideo.html#videos) is an “injured phoebe,” a bird described on the Cornell Lab of Ornithology website as “common and their numbers are stable or increasing in most areas.”
2. “Cat predation is one of the reasons why one in three American bird species are in decline,” claims ABC president George Fenwick. Where’s the evidence? Certainly not in Loyd’s study!
Indeed, in their contribution to The Domestic Cat: The Biology of Its Behaviour, researchers Mike Fitzgerald and Dennis Turner thoroughly reviewed 61 predation studies, concluding rather unambiguously that “there are few, if any studies apart from island ones that actually demonstrate that cats have reduced bird populations” (Fitzgerald & Turner, 2000).
Something else to keep in mind: predators—cats included—tend to prey on the young, the old, the weak and unhealthy. At least two studies have investigated this in great detail, revealing that birds killed by cats are, on average, significantly less healthy that birds killed through non-predatory events (e.g., collisions with windows or cars). (Møller & Erritzøe, 2000) and (Baker, Molony, Stone, Cuthill, & Harris, 2008).
As the UK’s Royal Society for the Protection of Birds notes: “Despite the large numbers of birds killed, there is no scientific evidence that predation by cats in gardens is having any impact on bird populations UK-wide… It is likely that most of the birds killed by cats would have died anyway from other causes before the next breeding season, so cats are unlikely to have a major impact on populations” (RSPB, 2011).
3. “If we extrapolate the results of this study across the country and include feral cats,” argues Fenwick, “we find that cats are likely killing more than 4 billion animals per year, including at least 500 million birds.”
But nobody claiming to have even the slightest regard for science would extrapolate from five birds killed in Athens, GA, for the purposes of developing a nationwide “estimate.” (No doubt Fenwick is, as is common practice at ABC, also inflating the number of outdoor cats for his calculations.)
The ABC/TWS press release is just the latest installment in the long-standing witch-hunt against free-roaming cats. It’s difficult not to see it as an act of desperation—no surprise, really, from organizations whose position is supported by neither the science nor public opinion.
Peter J. Wolf
http://www.VoxFelina.com
Literature Cited
• 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.
• Fitzgerald, B. M., & Turner, D. C. (2000). Hunting Behaviour 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 (2nd ed., pp. 151–175). Cambridge, U.K.; New York: Cambridge University Press.
• Møller, A. P., & Erritzøe, J. (2000). Predation against birds with low immunocompetence. Oecologia, 122(4), 500–504.
• Paluska, M. (2012). Kitty cameras show Athens cats on the prowl [Electronic Version], from http://www.cbsatlanta.com/story/17711012/kitty-cameras-show-athens-cats-on-the-prowl
• RSPB. (2011). Are cats causing bird declines? [Electronic Version]. Retrieved October 26, 2011, from http://www.rspb.org.uk/advice/gardening/unwantedvisitors/cats/birddeclines.aspx
• Shearer, L. (2012, April 24). Kitty cams show what Athens’ roaming cats are up to. Athens Banner-Herald, from http://onlineathens.com/local-news/2012-04-24/kitty-cams-show-what-athens-roaming-cats-are
Welcome to Life, Birds, and Everything. You can scarcely imagine my relief that you’re not this Peter Wolf.
Congratulations on mastering the creationist tactic known as the Gish Gallop. Thankfully, I don’t have to refute every point to demonstrate your lack of credibility.
As a scientist, I found these parts of your rant especially disheartening:
Ignoring for a moment the fact that it’s fundamental to the scientific method, do you think extrapolation is bad or good? Maybe bad when your enemies do it but good when you think it will serve your purposes? Why else would you extrapolate from studies conducted in the UK, where small wildlife species have evolved alongside Felis sylvestris [catus] since at least the Pleistocene, to North America, where the species has been present for less than 400 years and there is no similar native species, when you’ve denounced that very error on your own blog?:
Anyway, the extrapolation isn’t from five birds—it’s from 55 cats and 2000 hours of video, and the results corroborate similar studies.
Back to your comment. You asked (rather huffily):
If only you had been brave enough to explore all the resources in the Kitty Cam pages. Besides the Eastern Phoebe in the photo above, there were photos of a Hermit Thrush and a probable Northern Mockingbird nestling in the video presentation. The other bird victims must also have been natives, as the text states: “Only one of the vertebrates captured was a non-native species (a House Mouse).” This contradicts a common claim of cat hoarders that ferals do a service by eliminating pests.
But ignoring the evidence is small ethical potatoes compared to deliberately misquoting and misrepresenting an opponent’s argument, as you did to the American Bird Conservancy:
Maybe you shouldn’t have included that link, because anyone can read what the brochure actually says (emphasis mine):
That’s clearly percentages of “the wildlife cats kill,” not percentage of diet, yet you dig yourself in even deeper by making a wildly inappropriate comparison to coffee consumption.
But let’s return again to your comment:
That’s only unimpressive to someone who has trouble seeing the big picture. That 2000 hours of video amounts to about 37 hours per cat (with 5 of 60 cats not providing enough video to analyze). There are approximately 1.4 million times as many potentially predatory cats in the U.S. as in this study (see below for calculation). In the city of Athens alone, the researchers estimate that free-roaming cats are responsible for ~300,000 wildlife kills (including 40,000 birds) per year.
So let’s run some highly conservative numbers:
In this study:
55 free-roaming pet cats, 16 successful hunters (30%)
16 cats x 2.1 kills/week x 52 weeks/year = 1747 kills/yr
(1747 kills/year)/(55 cats in study) = 32 kills/FRP cat/yr
32 kills per FRP cat x 13% birds = 4 birds/FRP cat/yr
Extrapolation to U.S. cat populations:
86.4 million pet cats [APPA] x 31% allowed outdoors [you]) = 26.8 million FRP cats
26.8 million FRP cats + 50 million* feral/homeless cats [HSUS] = 76.8 potential cat predators
76.8 million potential cat predators x 32 kills/cat/year** = 2.44 billion animals killed/year
2.44 billion total animals killed x 13% birds*** = 317 million birds killed/year
*Conservative estimate; feralcatproject.org estimates 0.5 unowned cats/household (57.4 million), feralcats.org estimates 60 million, and ASPCA estimates 70 million.
**Proportion of successful hunters and kill rates per cat will necessarily be greater for feral/homeless cats (especially those in rural areas) and “barn cats” that are owned but unfed.
***The proportion of birds from this study, similar to bird predation rates observed in urban Wichita, KS (4.2 birds/cat/year, Fiore and Sullivan 2000); Crooks and Soulé (1999) calculated a rate of 15 birds/cat/year in southern California habitat fragments encroached by development.
To arrive at an estimate of “more than 4 billion animals per year, including at least 500 million birds,” Fenwick would have used higher figures for hunting success (appropriately—see ** and *** above), percentage of pet cats allowed outdoors (which could be double the figure I used), and/or feral/homeless cat populations. My estimates are lower than his because they’re based on numbers that would be more palatable to you, even if they are not as well supported by the evidence. The final question is: What level of needless carnage and ecosystem impoverishment must society tolerate in the name of abdicating responsibility for our pets and “saving” every last feral/homeless cat (while ignoring the millions of other homeless domestic animals that are euthanized each year)?
I can understand why you’re feeling so defensive about such a compelling study, and maybe toxoplasma is impairing your sense of ethics, but blatant dishonesty isn’t welcome on LB&E. If you have a rebuttal to my rebuttal, post it on your own blog.