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Measuring the mighty bear sense of smell

Posted by scott.weybright | October 25, 2017

“The bear’s sense of smell is the stuff of legend,” said Heiko Jansen, associate professor of integrative physiology and neuroscience at WSU. “Stories abound about them smelling things from miles away.”

a grizzly bear sniffs at one plastic tube and ignores another tube.
A bear at the WSU Bear Center takes an interest in one of the scents placed in a plastic tube as part of the olfactory experiment.

But legend and science are very different things, so Jansen and colleagues are working to quantify just how sensitive a bear’s sense of smell is, how it works, and what it may or may not be attracted to.

All through October, Jansen and his team have been exposing the bears at the WSU Bear Research, Education, and Conservation to a variety of different scents and measuring their reactions. The goal? Building a better bear spray.

“Current bear sprays can be harmful to bears and people,” Jansen said. “They’re pretty caustic. So, if we find something that just smells unpleasant to them and makes them think twice about approaching camp sites, for example, that would be really beneficial.”

White tubes are hung on fences at the Center, one with a scent and the other completely empty. They measure if a bear is attracted to, ignores, or is repelled by the scented tube. They also track how close or far away each bear goes.

Currently, each tube has five holes in it, allowing the scent to escape and spread quickly. Next year, once the bears wake up from hibernation, they’ll continue the experiment by gradually reducing the number of holes in each tube. This reduction will indicate how much odor is needed for a bear to catch the scent.

The study actually began two years ago, when they worked with the four cubs.

“We wanted to see if they had an innate reaction to certain scents,” Jansen said. “Since they were born at the Center, we knew they hadn’t been exposed to certain scents, like bear lure. So their reactions wouldn’t be biased by previous experiences.”

This month, they’re working with all 11 grizzlies at the Center to capture more data.

“If the adults respond similarly to the way the cubs did earlier, then we can be more confident that the response is innate,” Jansen said. “It gives us more confidence in our findings.”

Two years ago, the cubs responded most positively to eucalyptus, which contains pinene, a scent found in pine sap. Bear lure, which is made from blood gone rancid, also attracted the cubs. They avoided musk odors.

Ultimately, Jansen hopes this research will help to develop a scent that humans can tolerate but bears actively avoid—benefitting both.