Bear Studies

On the evening of August 13, 1967, two women were attacked and killed by grizzly bears (Ursus arctos horribilis) in separate incidents within Glacier National Park (GNP). Following these incidents, there was speculation that due to odors associated with menstruation, women may be more prone to attack by bears than are men (Rogers et al. 1991).

The objective of this paper is to present the data available on this subject so that women can make an informed choice when deciding whether or not to hike and/or camp in bear country during their menstrual period.

Polar Bears

In a study designed to test the hypothesis that bears are attracted to the odors of menstruation, Cushing (1983) reported that when presented with a series of different odors (including seal scents, other food scents, non menstrual human blood, and used tampons), four captive polar bears (Ursus maritimus) elicited a strong behavioral response only to seal scents and menstrual odors (used tampons).

Cushing (1983) also reported that free-ranging polar bears detected and consumed food scent samples and used tampons, but ignored non menstrual human blood and unused tampons. This suggests that polar bears are attracted to odors associated with menstrual blood.

Grizzly Bears

Herrero (1985) analyzed the circumstances of hundreds of grizzly bear attacks on humans, including the attacks on the two women in GNP, and concluded that there was no evidence linking menstruation to any of the attacks. The responses of grizzly bears to menstrual odors has not been studied experimentally.

Black Bears

Rogers et al. (1991) recorded the responses of 26 free-ranging black bears (Ursus americanus) to used tampons from 26 women and the responses of 20 free ranging black bears to four menstruating women at different days of their flow.

Menstrual odors were essentially ignored by black bears of all sex and age classes. In an extensive review of black bear attacks across North America, no instances of black bears attacking or being attracted to menstruating women was found (Cramond 1981, Herrero 1985, Rogers et al. 1991).

Yellowstone National Park Bear-Caused Human Injury Statistics

Over 62 million people visited Yellowstone National Park (YNP) during the 23 year period from 1980 through 2002. These visitors spent over 15.4 million use nights camping in developed area campgrounds and over 956,000 use nights camping in backcountry areas within the park. Although actual statistics are not available, many menstruating women undoubtedly visit, hike and/or camp within YNP each year.

During the 1980-2002 time period, 32 people were injured by bears within YNP, an average of only 1.4 bear-inflicted human injuries per year (Gunther 2003).

There was no evidence linking menstruation to any of these 32 bear attacks. Of these 32 injuries, 25 (78%) were men, and 7 (22%) were women.

Of the 7 women injured by bears, most (57%, n=4) involved surprise, close encounters between bears and women that were hiking and were therefore probably unrelated to menstruation.

In 3 (43%) incidents surprise encounters were not involved. Of these 3 incidents, 1 involved a female (non-menstruating) jogger in a developed area that was slowly approached then bitten by a grizzly bear, 1 (6%) involved a female Park Ranger moving an injured bear that had been hit by a car off of the road (thus was probably not related to menstruation), and 1 involved a woman (non-menstruating) in a tent in the backcountry.

It is difficult to accurately compare the ratio of males to females that are injured by bears because the park does not keep records of visitor use of the park by gender. However, the injury data for YNP does not suggest that females are more likely to be attacked by bears than are males (Gunther and Hoekstra 1996).


Although there is no evidence that grizzly and black bears are overly attracted to menstrual odors more than any other odor, certain precautions should be taken to reduce the risks of attack.

The following precautions are recommended:

1. Use pre-moistened, unscented cleaning towelettes.

2. Use internal tampons instead of external pads.

3. Do not bury tampons or pads (pack it in – pack it out). A bear may smell buried tampons or pads and dig them up. By providing bears a small food “reward”, this action may attract bears to other menstruating women.

4. Place all used tampons, pads, and towelettes in double zip-loc baggies and store them unavailable to bears, just as you would store food. This means hung at least 10 feet above the ground and 4 feet from the tree trunk.

5. Tampons can be burned in a campfire, but remember that it takes a very hot fire and considerable time to completely burn them. Any charred remains must be removed from the fire pit and stored with your other garbage. Also, burning of any garbage is odorous and may attract bears to your campsite.

6. Many feminine products are heavily scented. Use only unscented or lightly scented items. Cosmetics, perfumes, and deodorants are unnecessary and may act as an attractant to bears.

7. Follow food storage regulations and recommendations so you can avoid attracting a bear into your camp with other odors. All odorous items that may attract bears, including food, cooking and food storage gear, toiletries, and garbage, must be kept secured from bears.

Proper Methods for Storing Bear Attractants

1.) in a vehicle (the trunk of a car or cab of a truck)

2.) in a solid camping trailer that is constructed of non-pliable material (never in a tent or tent trailer)

3.) in a food storage box (provided at some campgrounds), or 4.) suspended at least 10 feet above the ground and 4 feet horizontally from the tree trunk.

The question whether menstruating women attract bears has not been completely answered (Byrd 1988).

There is no evidence that grizzlies are overly attracted to menstrual odors more than any other odor and there is no statistical evidence that known bear attacks have been related to menstruation (Byrd 1988). However, park visitors have been injured and killed by bears (Gunther and Hoekstra 1996).

If you are uncomfortable hiking and camping in bear country for any reason, you should probably choose another area for your recreational activities.

Literature Cited

Byrd, C.P. 1988. Of bears and women: Investigating the hypothesis that menstruation attracts bears. M.S. Thesis, Univ. Montana, Missoula. 129pp.

Cramond, M. 1981. Killer bears. Outdoor Life Books. Charles Scribner’s Sons, New York, N.Y. 301pp.

Cushing, B. 1983. Responses of polar bears to human menstrual odors. Int. Conf. Bear Res. and Manage. 5:270-274.

Gunther, K. A., and H. L. Hoekstra. 1996. Bear-inflicted human injuries in Yellowstone, 1970-1994, a cautionary and instructive guide to who gets hurt and why. Yellowstone Science 4(1):2-9.
_____. 1997.

Yellowstone National Park bear-related injuries/fatalities. Inf. Pap. No. BMO-1. U.S. Dep. Inter., Natl. Park Serv., Yellowstone National Park. 2pp.

Herrero, S.M. 1985. Bear attacks – their causes and avoidance. Winchester Press, New Century Publishers, Inc., Piscataway, N.J. 287pp.

Rogers, L.L., G. A. Wilker, and S.S. Scott. 1991. Reaction of black bears to human menstrual odors. J. Wildl. Manage. 55(4):632-634.


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