From 1980-2011, over 90 million people visited Yellowstone National Park. During the same 32 year period, 43 people were injured by bears in the park. For all park visitors combined, the chances of being injured by a bear are approximately 1 in 2.1 million. The probability is significantly lower for those visitors that don't leave park developments or roadsides, but much higher for those hiking in backcountry areas. When backcountry hiking, you can reduce the odds of being injured by a bear by: 1) hiking in groups of 3 or more people, 2) staying alert, 3) making noise in areas with poor visibility, 4) carrying bear spray, and 5) not running during encounters with bears.
Grizzly Bear-Inflicted Human Injuries
Grizzly bear-inflicted injuries to humans in developed areas averaged approximately 1 per year during the 1930s through the 1950s, and 4 per year during the 1960s. Grizzly bear-caused human injuries in developed areas then decreased to 1 injury every 2 years (0.5/year) during the 1970s. During the last 32 years (1980-2011), there have been only 3 (0.1/year) grizzly bear-caused human injuries in developed areas, an average of approximately 1 every eleven years.
During the 32 year period from 1980-2011, there have been 32 human injuries caused by grizzly bears in the backcountry, an average 1 per year. The park does not have statistics on how many park visitors hike in the backcountry, so the probability of being injured by a bear in backcountry areas cannot be calculated.
Black Bear-Inflicted Human Injuries
Human injuries caused by black bears have decreased from averages of 46 per year from 1931-1969, to 4 per year during the 1970s, and less than one (0.2) per year from 1980-2011 (approximately 1 every 6 yrs). Over the last 32 years, an additional 3 (0.1/year) bear-inflicted human injuries occurred where the species of bear could not be determined.
Bear-Caused Human Fatalities
During the 140-year (1872-2011) history of Yellowstone National Park, seven people have been killed by bears in the park. More people in the park have died from drowning, burns (after falling into thermal pools), and suicide than have been killed by bears. To put it in perspective, the probability of being killed by a bear in the park (7 incidents) is only slightly higher than the probability of being struck and killed by lightning (5 incidents).
- August 2011 - a day hiker, hiking by himself, was killed by a grizzly bear on the Mary Mountain Trail in Hayden Valley.
- July 2011 - a day hiker in a party of two was killed by an adult female grizzly bear with 2 cubs on the Wapiti Lake Trail in Hayden Valley.
- October 1986 - a photographer was killed by an adult female grizzly bear near Otter Creek in Hayden Valley.
- July 1984 - a grizzly bear killed a backpacker in a backcountry campsite located at the southern end of White Lake near Pelican Valley.
- June 1972 - an old adult female grizzly bear killed a man in an illegally established camp. The man surprised the bear when he returned to his campsite at night. The bear was in his camp feeding on food that he had left out unsecured in the campsite.
- August 1942 - a bear killed a woman at night in the Old Faithful campground. The species of bear involved was not determined.
- 1916 - a grizzly bear killed a man in a roadside camp.
- A possible fatality supposedly occurred in 1907 when a man was attacked by a female grizzly bear after he prodded her cub with an umbrella. The account of the incident appeared in a popular book, "Book of a Hundred Bears" published in 1909 by F.D. Smith. However, the validity of this incident is questionable as there is no mention of it in official park reports or local newspapers from 1907. The "Book of a Hundred Bears" contains many stories without providing back-up documentation. The 1907 story appears to be an unsubstantiated legend.