A new study in the Journal of Experimental Biology says that there’s a good reason that hikers encounter grizzly bears on trails: It seems that the path of least resistance for grizzlies is the same one that humans like to walk on.
Grizzly bears on a treadmill
For the study, researchers at Washington State University’s Bear Research, Education, and Conservation Center trained nine captive bears to walk and run on a custom, air-tight horse treadmill. In addition to being a level walking surface, the steel and polycarbonate treadmill could also be pitched up or down. The reason it was air-tight was so scientists could measure the amount of oxygen used by bears as they walked. This info, in turn, allowed researchers to estimate calorie consumption.
Of course, a whole lot of persuasion was needed (just like with most humans) to get the bears on the treadmill. It took two months of training—plus a steady stream of treats such as apples, dog biscuits, and hot dogs once the bears were on the treadmill. “The most stressful part of rewarding them was ensuring that the apple slice didn’t fall, resulting in the bear turning around on the treadmill to go after it,” said Anthony Carnahan, a lead author on the study.
For the Center’s bear, the most energy-efficient walking speed was about 2.6 miles per hour. This data was then compared with tracking data from 30 GPS collar-wearing grizzlies in and around Yellowstone National Park. The Yellowstone bears typically walk at a leisurely 1.2 mph. Of course, the park bears were not on a steady diet of hot dogs and apples; they were actively looking for their next meal.
And grizzlies spend most of their time feeding, especially during autumn when they are gaining weight before hibernation. The Yellowstone grizzly diet is not a picky one—the National Park Service estimates that these bears consume, at least, 266 species of plant, fish, invertebrate, mammal, and fungi.
Sharing the same hiking trails
While building up energy for winter, it makes sense that wild bears are trying to expend as little as possible. And this is where the WSU study factors into your next fall hike: The treadmill bears needed increased energy to go up and down steep slopes. It makes sense that their wild counterparts pick flat paths or ones with shallow slopes, preferably no more than a 10 percent grade up or down.
In 2019, there were 28 reported grizzly encounters on Yellowstone backcountry trails (and no visitors were injured). Yellowstone National Park also has rules for hiking in bear country. These include calls to: Be alert, hike in groups of three or more, make noise, and carry bear spray/know how to use bear spray. In addition, hikers are asked not to hike at dawn, dusk, or during the night, and not to expect bears to see you first.
And, remember, if you cross paths with a grizzly bear in the wild, it’s their path, too.
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