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Bear Aware: Why Some Say Spray

As snow accumulates over much of North America, droves of bears across North America are settled in for a long winter’s nap. Another bear season is behind us, but it won’t be long before spring, and bears, are back in our thoughts. Anyone who has ever traveled in bear country can relate to the rush of adrenaline that comes from simply seeing a huge bear print in the soil. Living in Alaska I would regularly see such prints, many of which were the size of dinner plates. They always served as a compelling reminder to keep my bear spray close at hand. I know, it sounds dubious to think pepper extract in an aerosol can could thwart the advance of a gigantic bear, but it does work and I’ll try to explain why.

To best understand how bear spray works, you have to first understand how a bear’s nose works, and to give you a rough idea just how powerful a bear’s nose is, consider this: A typical dog’s sense of smell is 100 times more sensitive than a human’s. A Bloodhound can smell 300 times better than the average dog, and a bear’s keen sense of smell is seven times better than that of a Bloodhound.

A bear’s nose is an amazing piece of bio-engineering with hundreds of tiny muscles that make it almost as dexterous as a human hand. A bear can twist and contort its nostrils to catch the faintest aromas. Those smells then travel up two nine inch channels with hundreds of times more surface area than a human’s to a spot where more than ten million nerve strands and a billion receptor cells fire electrical signals directly into the bear’s brain. Inside the bear’s brain is an olfactory bulb the size of a plum. A human’s is barely the size of a pea.

The end result is an animal that interacts with its home environment through a complex map based on smells. When a bear wants to go back to its den it knows to turn at the punky spruce tree, go beyond the sour ant hill, and then past the rotten mushroom patch. Famed Alaskan naturalist Greg Streveler once told me that when we walk by a restaurant we smell food. A bear could be a mile from that same restaurant and not just smell food, but each individual ingredient in the kitchen as well as the Tic-Tac in the mouth of the cook. I think you get the idea, a bear has a sharp sniffer.

Back to bear spray. Everyone agrees, you don’t snack on habanero peppers; they contain capsaicin, the component in peppers that makes your mouth burn and eyes water. In the most general terms, pepper heat is rated in a unit of measure called a SHU, or Scolville Heat Unit. A habanero scores about 250,000 SHU points. Bear spray, like that distributed by the makers of Counter Assault, rates 3.6 million on the SHU scale. Imagine what happens then when you take those 3.6 million SHU units and you shoot them up the highly sensitive snoot of a bear. To share more of Greg Streveler’s material, he said the best way to describe what it’s like for the bear being sprayed is to imagine you’re just going about your business and someone blasts a train horn next to your head. The words, “sensory overload” fall short. It’s not that it just burns the bear’s nose, it overwhelms its most delicate sensory system.

At this point, plenty of you are still skeptical, and I understand completely. Maybe some numbers will help. Renowned bear expert Tom Smith has written multiple papers on the subject of bears, spray, and other related topics. His research sampled 133 bear attacks that included bear spray and resulted in only three minor injuries. By contrast, a sample of 269 attacks whereby a gun was used for defense, the end results included 17 dead people. This is not to say you shouldn’t carry a gun for your defense, but statistics confirm that spray has been proven effective in real world situations, arguably with better results.

Bears are incredible animals and seeing one in the wild is not just a memorable spectacle, it’s an exhilarating experience. When that encounter gets too close for comfort, having a tiny can of bear spray won’t instill a great deal of confidence, but it will work. Just trust in the power of pepper and the sensitive science behind that big nose sizing you up.


Christophe Noel is a journalist from Prescott, Arizona. Born into a family of backcountry enthusiasts, Christophe grew up backpacking the mountains and deserts of the American West. An avid cyclist and bikepacker, he also has a passion for motorcycles, travel, food and overlanding.