“Cats Are Evil”: Just a Bit Simplistic

Posted on February 4, 2013


Reporters seem capable of focusing on only one simple concept at a time.  Okay, I get it; they only have so many seconds of air time, or so many column-inches available.  They probably try to keep their stories short to cater to our allegedly miniscule attention spans.  They don’t want to overburden us or muddy their own message by mentioning anything complicated.  And face it, some outlets are just plain biased.  The result: over-simplified stories and over-generalized conclusions, like… oh, here’s one:  “Cats Are Evil,” a particularly one-sided article in Slate.

Unfortunately, screaming, sensationalistic headlines and spotty reporting have an impact on public opinion, and in societies where we can contact our legislators, a misinformed public can make misguided demands, as we see is already happening in one province of Canada, and in New Zealand.  This is… well, scary.

The flurry of over-excited anti-cat headlines last week was prompted by a study by Scott Loss, Tom Will, and Peter Marra, claiming that as many as 3.7 billion US birds and 20.7 billion US mammals, to quote the top end of the estimates, are killed annually by cats.

We know that cats kill small creatures, but more than 20 billion annually in the US, really?  Can we check the veracity of this claim?

First let’s run a quick search of news headlines on cats killing birds.  That turns up many outlets reporting the same take on the very same study, but it also turns up those publications which question the conclusions.  This is the quickest, easiest way to get some balance in your news diet.

When reading any publication, though, one must also consider the source.  Do they have a vested interest in the topic?  Are they biased?  We will certainly get an opposing view from groups who advocate for feral cat rescues, but how objective will they be?  The same goes for bird-lovers’ organizations, who welcome this study unquestioningly.  As it turns out, several outlets have noted the academic link between two of the authors and a former colleague who was convicted of poisoning neighborhood cats.  Even if we separate the authors from her actions, the fact remains that they cite her previous academic work in their new study… and that unquestionably introduces a possible bias.

Bias aside, there is the science involved.  Is it sound?  How did these guys get their numbers?  Actually, their paper is just a survey of previous studies, and… oh, wait.  The same three authors collaborated on another paper just a few months ago, which focused on the lack of precise methods of quantifying bird mortality and assessing real biological impacts.  In plain English:  we have no friggin’ way of knowing exactly what is going on.  And yet, the authors cited the very same imprecise data from pre-existing literature for their new study, then extrapolated those small, uncertain data sets to encompass the whole of the continental United States.  Well – the farther one extrapolates uncertain figures, the more uncertain they become, wildly exaggerating even small inaccuracies.  In sum, the authors criticized the accuracy of existing data, used it anyway in their most recent paper, then extrapolated from it to arrive at huge numbers that are not even a good guess at reality.  Sorry, that’s what I call scientifically flawed.

Add to all of this the fact that bird populations have been in decline for decades, and many other studies implicate many factors:  habitat loss, water shortages, climate change, collisions with man-made objects, and disease, in addition to invasive species… of which the cat is but one.

Even supposing that the authors were correct and cats were responsible for all of this predation, and supposing that the cats could be magically and entirely removed, what then?  Consider a couple of historical footnotes.   First, humans and cats have been in a symbiotic relationship for millennia.  The “domestication” of the cat has been traced by genetic studies to about 10,000 years ago, in the same time and places that humans were developing agriculture and beginning to store grain.  Cats would have benefited by the easy prey of rodents attracted to the granaries, and humans would have benefited from the cats’ ability to reduce rodent spoilage of their grain stores.  Second, when we have tried to get rid of our little feline symbionts, we have generally not done well:  let’s fast-forward to Europe, when Pope Gregory IX issued a Papal Bulletin in 1232 declaring cats “diabolical.”  The following century, with the cat population at a low ebb, the rat population had exploded… and then the flea-borne bubonic plague broke out several times in quick succession, killing about a third of the human population in Europe.   It’s true that any mammal can support the fleas which carry the plague, but the sheer numbers of rats – and therefore fleas – were far greater than any cat population would have been.  Interesting that other societies, which valued cats for pest control, were not nearly as impacted by the plague as Europe was.

Even in modern times, the symbiotic relationship continues; in India, it has been noted that over the last few decades, the populations of native herbivores and carnivores – including cats – have “dwindled while those of the grainivorous opportunistic rodents have tended to increase,” with the result that about 5%-6% of each year’s grain crop is destroyed by rodents, in addition to significant rodent damage to produce and poultry.  Not to mention that India suffered a plague outbreak in 1994.  Apparently India could do with some more cats.

And then there is the symbiotic relationship much closer to home.  My neighbor’s barn was overrun with mice which were destroying her hay stocks; now she has two cats, no hay spoilage,  and rarely sees a mouse.  Being in a rural area, we do get the occasional mice in our house; our three cats take care of that quite handily.  When sensationalist headlines wail over the many furry creatures that cats kill annually, we should keep in mind that some of that is actually good for us.