Do We Really Know That Cats Kill By The Billions? Not So Fast [View all]

[Kelvin Mace]

http://www.npr.org/blogs/13.7/2013/02/03/170851048/do-we-really-know-that-cats-kill-by-the-billions-not-so-fast

On NBC Nightly News on Thursday evening, Brian Williams there's a backlash underway to all the of this past week.

Cats are hunters and other creatures do fall prey to them in significant numbers.

And yet there are serious reasons to suspect the reliability of the new, extreme cat-killer statistics.

The study at issue is a meta-analysis, an overarching review that aggregates data from previously published sources. The accuracy of meta-studies in health and medicine raises some , and it's easy to see why: for a meta-analysis to be solid, wise choices must be made among the available sources of information, and results that may vary wildly must be weighed fairly.

In the Nature Communications study, authors Scott R. Loss, Tom Will, and Peter P. Marra needed to incorporate into their model the number of "un-owned cats" (such as stray, feral, and barn cats) in the U.S. As they note in to the article, "no empirically driven estimate of un-owned cat abundance exists for the contiguous U.S." Estimates that are available range from 20-120 million, with 60-100 million being the most commonly cited. In response to this huge uncertainty in the numbers, they performed mathematical calculations using what they feel to be a conservative figure (specifically, they "defined a uniform distribution with minimum and maximum of 30 and 80 million, respectively.&quot

At this juncture, the authors note that local analyses of cat numbers are "often conducted in areas with above average density." That is an obvious problem, yet when they estimated the proportion of owned cats with access to the outdoors (and thus to hunting), of eight sources of information, "three [were] based on nationwide pet-owner surveys and five based on research in individual study areas." Are the local studies representative of the national situation? For that matter, are the different owner surveys administered in a consistent enough manner to allow them to be aggregated?

Of course, the authors make statistical perturbations designed to increase the reliability of their conclusions, but it seems to me there's an unsettling degree of uncertainty in the study's key numbers.

Demonizing cats with shaky statistics, however, won't help us build the pillar of understanding required to strike a satisfying balance between the needs of cats and their supporters with the needs of wildlife facing a feline threat.

See also:

http://www.kcet.org/news/rewire/wildlife/4-reasons-cats-bird-kills-dont-excuse-wind-turbine-bird-kills.html
http://www.rspb.org.uk/advice/gardening/unwantedvisitors/cats/birddeclines.aspx
http://www.chicagonow.com/steve-dales-pet-world/2013/05/without-cats-birds-would-suffer-so-would-we/
http://www.philly.com/philly/blogs/pets/Cat-defenders-protest-Smithsonian-backing-of-controversial-study.html

Call me when the cat killer study is peer-reviewed. A meta-analysis can be easily skewed based on what studies you decide to include.

Yes, I own a cat, and dogs, and have rescued other injured creatures such as rabbits, possums, and geese for rehabilitation and release. My cats have always been kept indoors which is why I have had a number of cats who lived 20+ years.