09/18/2026
For campers spray their tents with bear repellent to keep curious bears away: A 20-year review of Alaska bear spray incidents found 11 cases where the residue did the opposite and drew bears in.
Tom Smith, a wildlife biologist with the U.S. Geological Survey's Alaska Science Center, first noticed the problem when he watched a brown bear roll vigorously in beach gravel that had accidentally been sprayed with red pepper spray.
The bear was not fleeing the chemical designed to repel it. It was luxuriating in it, coating its fur the way a dog rolls in something dead. Smith had spent years documenting how effectively bear spray stopped aggressive bears in real encounters. This was the opposite reaction, and it sent him back into the field to find out how often it happened.
Bear spray is a pressurized aerosol containing oleoresin capsicum, the compound that makes chili peppers burn. Fired directly at a charging bear's face, it works. Smith's later 20-year review of bear spray incidents across Alaska, published in the Journal of Wildlife Management in 2008, analyzed 83 cases between 1985 and 2006 and found the spray stopped aggressive behavior 92 percent of the time in brown bears, 90 percent in black bears, and both recorded polar bear cases. Ninety-eight percent of the 175 people involved in these encounters walked away uninjured. Smith would later say the spray had saved his own safety a number of times in the field.
But firing spray at a charging animal and applying spray to an object are two different actions with two different chemical outcomes, and campers had been treating them as interchangeable.
Word had spread that spraying a tent, a cooler, or the perimeter of a campsite with bear spray would keep curious bears away, the same way a repellent keeps mosquitoes off skin. Smith's pilot study, prompted by the beach gravel incident, set out to test that assumption directly. He established sites and applied red pepper spray to them under controlled conditions, then documented how brown bears responded when they encountered the residue.
The responses ranged from mere sniffing to whole-body rolling in the residues. Some bears investigated briefly and moved on. Others treated the sprayed ground the way bears treat a scent-marking tree, a carcass, or another bear's rub site: something worth extended physical contact. A bear rolling in pepper spray residue is engaging with the smell, not avoiding it.
The 20-year review confirmed the pattern was not a one-off curiosity. Smith and his co-authors documented 11 separate incidents in which bear spray applied to objects with the specific intent of repelling curious bears backfired and drew bears in instead.
The broader 83-incident dataset the review was built from involved brown bears in the large majority of cases, with black bears making up most of the remainder. The study's authors were explicit that the residue finding applied only to spray left on tents, packs, coolers, and campsite perimeters, not to spray discharged directly at a bear during an encounter.
A thin residue left to dry on canvas or nylon does not deliver that same overwhelming dose. It leaves behind a persistent, diffuse scent that a bear's nose, thousands of times more sensitive than a human's, can investigate at leisure without the accompanying blast of concentrated capsicum that would normally drive it away.
Smith's sample of 11 backfire incidents was small, and the study did not compare outcomes across different commercial spray brands. But the pattern was consistent enough that Smith advised campers against the practice directly and recommended that hikers only test their spray cans, if they wanted practice with the discharge mechanism, before entering bear country rather than around the tent they planned to sleep in that night.
Image is for illustration purposes only
Source: Smith (1998), Wildlife Society Bulletin / Smith, Herrero, Debruyn, and Wilder (2008), Journal of Wildlife Management / ScienceDaily / EurekAlert / CBC News / USGS Alaska Science Center.
