The Majority Of Mountain Lions Are After Your Beloved Pets. Or Are They?

Tuesday, 16 February 2016.

"Study finds mountain lions are feasting on pets" says the worrisome headline above the Chronicle's Tom Stienstra's article in SFGate this weekend. In it he shares how the Department of Fish and Wildlife shared with him a study that "had not been released to the public". The results of the study were shocking: 52% of 107 mountain lions killed under depredation licenses were found to have cats and dogs in their stomachs! Only 5% of mountain lions were found to have eaten deer, despite the fact that deer are "supposed to be their favorite prey."

When I read the study, I was surprised to learn that the original data doesn't mention pets, cats or dogs at all.

Soon the story spread across local and national news, all quoting Stienstra and some even going further than the details Stienstra shared. The comment sections filled up with calls to remove hunting limitations. Here is just a small selection as the story continues to spread throughout the internet:

Stienstra, who holds a degree in journalism and has received multiple awards for his outdoor writing, fails to provide basic information. He doesn't mention, for example, the region in which the mountain lions were killed. To make matters worse, after reading a copy of the study that was kindly provided to me by the DFW, I found that it requires a good dose of imagination to come to the conclusion that mountain lions are collectively targeting your beloved house pets. For example, I was surprised to learn that the original data doesn't mention pets, cats or dogs at all.

So what is in the study? Rather than taking my word for it, I'll provide the raw data. It isn't much, but here it is:

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So what can we learn from it? What does the "study" (or rather, this small set of observations) actually say?

At first glance, the numbers seem to be very similar to what Stienstra reported and we can now add a location: these mountain lions were killed in 2015 in various CDFW regions in California.

But when you look closer, the data says something completely different from Stienstra's warning to all pet owners. First of all, it deals with a very "loaded" data set that is in no way a representation of the entire mountain lion population in California or anywhere else. Stienstra mentions, but never clarifies the term "depredation permit" in his article. It is illegal to kill mountain lions in California, except for under special depredation permits. The California DFW explains it as follows on their website: "Those [mountain lions] that prey on pets or livestock can be killed by a property owner after the required depredation permit is secured."

All the mountain lions in this study were taken under depredation permits, so they were all killed BECAUSE they ate pets or livestock. So what you'd expect is to find remains of domestic animals in the vast majority, if not all of the mountain lions killed under such a permit.

Instead, the stomach contents of the 107 killed mountain lions were divided as depicted in the chart below:

In his article Stienstra goes on to speculate that if the 16% of stomachs that were not studied also contained pets, the total number of lions eating pets could be as high as 60%.

Despite Stienstra writing repeatedly that the study details that "cats and dogs and other domestic animals" were found in 52% of the mountain lions, the study itself only speaks of "domestic animals." I inquired with the DFW if the study made any distinction between livestock and pets when they studied the stomach contents and they responded that while cat and dog remains were present in some necropsied mountain lions, the exact details of which type of domestic animal was found in each mountain lion were not recorded.

Interpreting this same dataset differently could just as easily lead to the conclusion that 48% of mountain lions killed under depredation permits were not found guilty after their execution.

In summary, the study says that 52% of 107 mountain lions killed because they were suspected of eating domestic animals were found to actually contain domestic animals, whether that be chickens, goats, sheep, cows, rabbits, circus elephants or, indeed, cats and dogs. Interpreting this same dataset differently could just as easily lead to the conclusion that 48% of mountain lions killed under depredation permits were not found guilty after their execution.

That's it. That's all there is to be said about this not-so-noteworthy data set. The study itself doesn't provide any conclusion beyond the raw data, there is no talk of a trend, no comparison to data from previous years and no talk about "house pets". Yet we read in the news that mountain lions are feasting on our cats and dogs more than before.

So why does it matter if Stienstra gets creative with the results of this study? Not only the public, but other news outlets see him as a reliable source with great knowledge of California wildlife. And why wouldn't they? Sure, it is an unfortunate but accepted phenomenon that scientific studies and statistics are hard to communicate to the public and can be cherry-picked and exaggerated by journalists to gain online clicks. But for a piece to so blatantly misrepresent facts in a newspaper article borders on the unethical.

People who come across the story without context won't know that it is not the first time that Stienstra has vilified predators in an article that he -or the newspaper that carried it- failed to identify as an opinion piece, and presented as fact. In an article last year, that offers a glimpse of what may have influenced his current interpretation of the DFW's data, he detailed how his own pet was taken by predators. In the following paragraphs he made no effort to detach his personal emotions as he veered in and out of anecdotes, unscientific conclusions based on personal observations and numbers provided without a source all seemingly leading to the conclusion that predators are a curse on, rather than a part of, every ecosystem.

People who read the article might also not realize that it is not the first time Stienstra has been undeniably wrong about facts. Only last week he reported a sighting of a lynx in the Bay Area, when a hiker claimed to have seen a mountain lion, a bobcat and a lynx in one day, an occurrence triumphantly dubbed a" Bay Area Wildlife Triple Crown" by Stienstra. After readers pointed out that lynxes don't live anywhere near California, Stienstra explained that in fact the person had observed a mountain lion, a bobcat and another bobcat, but never updated the article, so the wrong information still lives on in cyberspace.

And that is one of the main problems with seemingly trustworthy articles that misrepresent facts. Despite the fact that some news articles are factually wrong, even when the errors are addressed at a later time or disputed by experts on the web, bad news spreads online and stays online. Hundreds of thousands of people will read Stientra's article or a derivative of it. Those readers have every reason to believe that mountain lions are in fact coming for their pets at an alarming and increasing rate, while no longer preying on deer. The fact that Stienstra's article doesn't mention a location makes it easy for opinion makers in every state to point to the study as if it applies to their own local situation.

News articles concerning predators contribute to public opinion, which in turn plays into the hands of the hunting lobby, anti-conservationists and others who influence opinion makers and law makers in California and beyond. To keep mountain lions protected and value them appropriately as the largely elusive top-predators that they are, it is important to stick to the truth and nothing but the truth. While scientists work hard to provide balanced ecological data to show what a truly healthy and safe mountain lion population looks like, fear mongering journalists feed the public stories and make them think the only good mountain lion is a dead one. And that's a sad state of affairs.

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