February 17, 2010 - 7:39 PM CST

Bears have killed people.  We’ve been focusing on that for a few days now, which might make us as bad as the sensational media that mischaracterizes bears by focusing on the rare attacks.  Our purpose is to refute misconceptions and promote understanding.  People often tell us we should frequently warn people about bears in order to avoid liability issues.  We prefer to simply tell the truth.

The misconception for today is the notion that menstrual odors trigger bear attacks.  How did that idea ever start?  It’s a story of bad science, a rush to judgment, and more worries about liability issues.  It’s also a story of a grizzly bear whose behavior is an exception to the pattern we’ve shown in previous updates.

At dusk on August 13, 1967, the grizzly came into a camping area in Glacier National Park, as it often did.  The campers were 2 women (both menstruating), 3 men, and a dog.  The bear was most interested in the hot dogs and fish the campers were cooking, so the campers moved their sleeping bags down to the beach to sleep.  During the night, the bear investigated the campers.  They awoke, rushed about, and climbed trees.  Michele Koons couldn’t unzip her sleeping bag and was killed. 

Dave Smith, author of Backcountry Bear Basics investigated the tragedy and raised some questions about the rush to judgment about menstruation.  Why was Michele Koons the last person the bear investigated?  If menstrual odors were the attraction, why did the bear investigate the men first instead of going straight for the two menstruating women?  When the bear attacked Michele Koons, was it because of cooking odors on her clothes?  Was it her heavy use of cosmetics?  Was it because she was menstruating? Or was it any of a host of other factors one could list?  How could park officials pick out one factor and say it was the cause?

They may have been influenced by another tragedy in Glacier NP the same night—a night that made the date infamous as “the night of the grizzlies.”  Another grizzly killed another young woman, and, although she was not menstruating, she had tampons in her purse.  It seemed like evidence enough.  The notion began.

The notion got a boost in 1980 when a young researcher presented various substances to polar bears and noted that the bears preferred used tampons over non-menstrual human blood.   However, he also reported that the bears retreated from menstruating women who stood outside polar bear cages.

Park Service officials were in a quandary.  Worried about liability, they distributed brochures warning women about camping or hiking in bear country while menstruating.  But to avoid complaints about differential treatment of women, they allowed female rangers to do the very thing they warned campers not to do.

Researcher Carolyn Byrd re-examined the results of the polar bear study and raised questions about the science.  Among other things, she said that menstruating women do not smell like used tampons that have been exposed to the air for some time.

No other study was done until 1990 when researchers from the Wildlife Research Institute recorded reactions of 26 free-ranging black bears to tampons from 26 women and recorded responses of 20 free-ranging bears to 4 menstruating women near Ely, Minnesota.  They found that “Menstrual odors were essentially ignored by black bears of all ages and either sex, regardless of season or the bear's reproductive status.”  The researchers also asked over 300 bear biologists at an international bear conference if any had heard of a black bear attacking a menstruating woman.   None had.  The researchers did an extensive review of black bear attacks across North America and found no instance of black bears attacking or being attracted to menstruating women.


Byrd, Caroline.  1988.  Of bears and women: investigating the hypothesis that menstruation attracts bears.  MS Thesis.  University of Montana, Missoula.

Cushing, Bruce.  1980.  The effects of human menstrual odors … on polar bears.  MS Thesis.  University of Montana, Missoula.

Rogers, L. L., G. A. Wilker, and S. S. Scott. 1991.  Reactions of black bears to human menstrual odors.  Journal of Wildlife Management 55(4):632-634.

Smith, Dave.  2006.  Backcountry bear basics.  The Mountaineers Books.  157 pages.


Again, thank you for your contributions and purchases.  Today, we added the picture of Lily as a framable 8x10 portrait.  We used archival ink on high quality luster paper.  We love this familiar picture of Lily’s pretty face and gentle eyes and dirt on her nose from her den construction last fall.  Lily is not available to sign it, so we thought we'd write her name small in gold unless we see in Facebook that you'd rather we didn't.   

As arrangements progress for the great Lilypad picnic gathering, we are really looking forward to meeting you at the campfire at the Bear Center.

—Lynn Rogers and Sue Mansfield, Biologists, North American Bear Center