Quirks & Quarks

Grizzly Tinder: Bears rubbing up against trees may be their dating calling card

Researchers always suspected bears rubbed trees to communicate, but didn't know what was being said. Now, a new study is the first to find a link between rubbing trees and mating success.

Researchers always suspected bears rubbed trees to communicate, but didn't know what was being said

In a new study, researchers found that bears who rubbed trees the most, would also have the most mates and the most offspring. (SVEN HOPPE/DPA/AFP via Getty Images)

Originally published on March 20, 2021.

Bears are known for enthusiastically scratching their backs on trees, but scientists haven't really known whether they're just scratching an itch, or if there's something more at play. Now a new study suggests there is a link between rubbing trees and reproductive success.

"We sort of assumed it was some form of communication. Bears are wide ranging, they are solitary, they have overlapping home ranges," Andrea Morehouse told Quirks & Quarks host Bob McDonald. "So it certainly seemed reasonable that they would use some form of olfactory or chemical signaling to communicate with other bears. But we didn't really have a lot of data to suggest exactly what was going on there."

In these trail camera images, a grizzly bear can be seen rubbing its back vigorously on a tree. (Andrea Morehouse)

After using rub trees to study the genotypes of over 2000 bears across Alberta, BC, and Montana, Morehouse and her colleagues discovered that bears that rub trees more often, have more mates, and produce more offspring. 

"We suspect that that as they're rubbing, they're relaying information about their condition, how dominant they are, how competitive they are, there's probably some also some information about their genetic makeup. And all of that information might be important, particularly for for females as they're deciding who to mate with." 

Morehouse is an independent scientist with Winisk Research and Consulting. You can listen to her conversation with McDonald at the link above.

Produced and written by Amanda Buckiewicz


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