Friday, 1 August 2008

Efficacy of Bear Spray.

You might have heard on the news, a while back, about a study showing Bear spray pretty darn effective at stopping bears of all species. The paper's by Smith et. al 2008. Bear spray is a souped up version of pepper spray, intended for use by hikers, hunters, and pretty much anyone having to live or work in bear country. The idea is that these Capsaicinoid sprays induce the same host of responses that occur when humans are sprayed - coughing, blindness, discomfort, etc (Miller 2001). Based on results with captive bears, a gentleman named David Miller (whom I can no longer locate, but was last seen at Colorado State University) recommended these high intensity sprays be considered as bear deterrent (Miller 1980).

I'll go out on a limb and lay out my biases: I'm for bear spray. I don't carry it myself, but I think makes a fine alternative to carrying a lethal weapon. With bear spray, both the bear and the user gets to go home at the end of the day, and the bear is unlikely to try to start things again, and I like that. That said, Smith et. al need to revisit their methodology.

My problems with their study, in a nutshell:
A) Dead men tell no tales. That's right, they couldn't interview anyone who used bear spray unsuccessfully and died. How frequent is this? I don't know! I don't think the dead people are going to be talking much about it. We do know, however, that bear fatalities occur. And we know it's slippery to try and figure out how many fatalities occur, because of the beyond-the-grave reporting issues.

Absently, I wonder what Timothy Treadwell's listed cause of attack is. I'm banking on `provoked.`

B) Bear spray is effective... compared to what? I don't see any good descriptive statistics here. Are they better or worse than doing nothing? This might sound crazy, but a number of the bear-human incidents in the study looked like they might have resolved themselves without the bear spray just as well as with! How does Bear Spray compare to fire arms? Better or worse? If we're going to make public safety recommendations based off of this study, we need to know how these categories stack against each-other. You can't analyse bear spray's effectiveness without groups of comparison.

Now. I still think bear spray is effective and worthwhile. This publication was just highly ineffective in demonstrating it.

While we're on the subject - there's a vicious rumour that polar bears are the most deadly of the bears. I hear people talk about how Polar Bears actively hunt humans, are drawn to humans in a hostile way, etc. USGS's own data, over 100 years worth, contradicts this view. In Alaska, Brown Bears make up 23% of the population, they write, but but make 86.4% of the conflicts. USGS reports this is 375% the expected if conflicts were randomly distributed across bear species. Polar Bears, to contrast, are only 30% of expected if conflicts were random, and represented only 1.5% of the conflicts in the state.

Miller, D.S. (2001). Review of oleoresin capsicum (pepper) sprays for self-defense against captive wildlife. Zoo Biology, v.20, pp. 389-398.
Miller G. D. (1980). Behavioral and physiological characteristics of grizzly and polar bears, and their relation to bear repellents. Thesis, University of Montana. Missoula, USA.
Smith, T.S., Herrero, S., Debruyn, T.D., and Wilder, J.M. (2008). Efficacy of Bear Deterrent Spray in Alaska. Journal of Wildlife Mannagement, v.72, pp.640-645.

Edit to add I've been told that the two Millers are not the same people. D.S. Miller didn't pioneer use of bear spray. Scientists can be tricky to track with just their initials.


Anonymous said...

What the? What was all that babbling about? You use it right? You read the report right? Simply put in laymen terms, bear spray is more effective than a gun or nothing. JEEEEEZ

KC said...

To Anonymous: No, Smith et. al (2008) did not make any such comparisons. Other authors might have, but not in this publication. I have read the paper, and I can state that firearms, guns, rifles, handguns, and any such other premutation of the concept was mentioned twice in the whole paper.

Once, in the introduction. Quote:
"People rely on a variety of deterrents for protection from bears, including firearms, red pepper sprays, signal flares, incendiary screamers, and an assortment of noise makers (Herrero 2002)."

The other time, in the conclusion. Quote:
"In portions of North America where bears are in decline managers may reduce the number of bears killed in defense- of-life by arming employees with bear deterrent sprays in addition to firearms."

Now. Feel free to prove me wrong. Otherwise, my points stand.

And, that `babbling on` was me quibbling with the science as a scientist. Their methodology is rocky. It relies on self-reports. That raises a giant flag for me as a Wildlife Biologist, whenever I see it. Quibbling is what scientists do. It's not just my right, it's a god-given duty.

Anonymous said...

I am a huge advocate of bear spray, know many people who have used it, either by provoking or by surprise with great results. Also know quite a few scientists and biologist who use it and it only.
Noise makers are exactly that. I don't go hiking in the back country to listen to a bunch a bear bells that only I can hear and the bears could care less about. Firearms, illegal. I wouldn't carry anyway, not because of bears if i ever did. It takes about 3 to 4 shots to take down a bear. Red pepper spray only seasons whence it falls. Signal Flares, I leave in the car.
Managers are required to carry guns. I have not met a park ranger or warden who doesn't reach for the spray first.

Anonymous said...

Try this, not having great results posting this.

Anonymous said...

Anonymous said...

KC said...

That not only isn't the publication I'm talking about, it isn't even close to the publication I'm talking about. I'm talking about Smith et. al 2008, and no one else. Anyone else I'll take on the merits of their research, but I'm blogging about a peer-reviewed article in the scientific journal "Journal of Wildlife Management."

I'm not arguing you shouldn't carry bear spray. I'm for it. I'm very pro-bear spray. I think it's effective and a boon to wildlife managers in the lower 48 (indeed, up here in AK too, since minimizing DLOP should be a goal). Go back, and re-read my post. You'll see I'm talking about This study alone. If you have something useful to say about my critique of their methodology, I'd be interested, but I'm not even /close/ to arguing against Bear Spray. Just that Smith et. al have poor methodology.

Anonymous said...

KC, what is wrong with the report exactly. It was done by 4 people, noting that Smith starts the report with "we". Both Smith, DeBruyn and Herrero are very well respected scientists who study bears. There are more studies being done with bear spray as we speak, hopefully more in depth. I believe I might have misread your comment but I would like to drive home that bear spray is the best choice. I am glad you agree.

KC said...

I know who Tom Smith is. The strength of this other research doesn't change the fact that he has NO ROOTED COMPARISON to demonstrate efficacy. Reputation has no bearing on truth value. Period

When you do clinical trials, you compare to a placebo or sham. In this instance, they should have compared it to self-reports of human-bear incidents without any aid, and followed the outcome. They shouldn't have relied on self-reports to generate their data, they should have done random questionnaires. They should estimate human mortality of individuals with bear spray from death records, which they did not do.

I don't think you've read my post at all. I think you saw I'm criticizing a study, and have leaped to conclusions.

Anonymous said...