They’re called rub or mark trees and are used by bears for more than simply scratching their backs. One BC study on grizzlies suggested that adult male bears in particular rub on certain trees to communicate with other bears, perhaps as a way of avoiding confrontations. As researcher Owen Nevin told ScienceDaily: “Big male bears can seriously injure and even kill each other when they get into a fight. If one recognizes the other from the scent marks on the rub trees in the area he knows he’s in for a tough fight — he’s on the other guy’s patch so to speak — so it might be better to back away than make a serious challenge.”

Another grizzly study from BC and Montana headed by Andrea Morehouse "found a positive relationship between bear rubbing behavior and reproductive success; both male and female bears with a greater number of mates and a greater number of offspring were detected at more rub objects and during more occasions. Our results suggest a fitness component to bear rubbing, indicate that rubbing is adaptive, and provide insight into a poorly understood behaviour."

Bears may also bite and scratch these same trees to leave their calling cards. You can see strips of bark removed in this Andy Peebles video from North Cowichan.

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— Oct. 13, 2021