Smith's team, which included Stephen Herrero, a world authority on bear attacks, has studied 600 bear encounters in Alaska over two decades. In 72 incidents in which bear spray was used properly, the bear stopped charging more than 90 percent of the time, according to a study Smith published in the April edition of the Journal of Wildlife Management. People using guns, by contrast, stood a one-in-three chance of failing to deter the bear, according to an earlier study.
"The probability is the bear spray will outperform a firearm and it's easy to see why. The spray is easy to deploy. The rifle is just difficult to use," Smith said. Stopping a charging bear with bullets required, on average, four hits.
Most of the 72 bear spray deployments Smith studied involved grizzly bears; the rest were black and polar bears. His team studied newspaper accounts, anecdotes and reports from wildlife agencies to determine the bears' activity before being sprayed, the distance involved, time of day, wind effects, mechanical problems and dosage of spray. Of the 150 people involved, just three injuries were reported and none required hospitalization.
"Tom is the best person to do this study because he has so much hands-on experience with bears," said Chuck Bartlebaugh, a vocal bear-spray advocate who leads the Center for Wildlife Information in Missoula, Mont. "We need a similar study done for the Intermountain region with inland grizzly bears who tend to be more aggressive because they don't have the salmon runs."
Last year was the worst on record for human-bear conflicts in Utah, with 203 black bear encounters, including a fatal mauling in American Fork Canyon. That total was substantially higher than in the previous four years combined, probably the result of poor natural food sources and a high number of fledgling juveniles leaving their home turf, according to Kevin Bunnell, large-mammal coordinator for the Division of Wildlife Resources.
Utah's wet winter bodes well for the coming season, "but it can turn south in a hurry," Bunnell said. "A single late freeze can have a big impact. So can a hot, dry July or August."
Smith's findings should debunk common reasons given for not carrying bear spray, which Smith calls ''an olfactory assault weapon.'' Although wind can interfere with spray accuracy, wind rarely reduced the spray's effectiveness, probably because most discharges occur in wooded areas and the spray exits the nozzle at 70 mph. His team found no instances in which the spray malfunctioned and only two instances in which the sprayers incapacitated themselves.
"Bear spray diffuses potentially dangerous situations in the short term by providing the user time to move out of harm's way and allowing the bear time to reassess the situation and move on," Smith wrote. "When food or garbage is involved with bear conflict, bear spray is effective initially, but one can expect bears to continue returning until these attractants are removed or otherwise secured."
Smith's study, funded by his former employer, the U.S. Geological Society and the Alaska Science Center, shows that bear spray can help conserve grizzlies, protected as a threatened species.
Every fall in the lands around Glacier and Yellowstone national parks, elk hunters kill grizzly bears in self-defense. According to the U.S. Fish and Wildlife Service, between 1980 and 2002, 49 grizzlies were fatally shot by people protecting themselves around Yellowstone (accounting for nearly one in six of all known bear deaths). Another 23 were shot around Glacier.
"In most cases there are no attempts to carry bear spray, much less use it. Every time a hunter decides to shoot instead of use bear spray they are making a decision they are going to set back grizzly bear recovery," said Brian Peck, of the Great Bear Foundation. "Had those people used bear spray, not only would [the bears] be alive, they would know that this red hot spray stuff will be really nasty and to avoid it and they would pass this information on. Bears are smart."