In August 1967 in Glacier National Park, 2 young women were killed by 2 different grizzly bears on the same night. One of the women was wearing cosmetics and was menstruating and using external pads. Some writers speculated that menstrual odors triggered the attack and bear-safety brochures now often warn women not to hike or camp in bear country during menstruation.
While also unlikely that 2 bears would attack on the same night without a common environmental event, the most important factor was probably the habituation of both bears to people and human-associated foods. A subsequent fatal attack at Glacier in 1976 involved a grizzly which entered a tent, dragging out and killing a young woman.
The woman was not menstruating or using cosmetics and the camp was sanitary. Two young male bears with a history of harassing campers were killed nearby a few hours later. In Yellowstone, 19 people were injured by bears between 1980-1994. Five victims were women; no evidence linked menstruation to any attack. More>