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Science  14 Sep 2007:
Vol. 317, Issue 5844, pp. 1477d
DOI: 10.1126/science.317.5844.1477d

Why does a bear rub in the woods? This giant grizzly bear from the forests of British Columbia had his tree-rubbing habits scrutinized as part of a project to get to the bottom of the question. It seems that bears engage in scent marking, rubbing, biting, and scratching the same trees over many seasons. Once a bear has “anointed” a tree, others follow suit—in fact, stepping in the same tracks. To learn more, Owen Nevin, now at the University of Cumbria in Wales, set up cameras in four bear-rubbing trees and recorded 52 bear events on spring nights in 2005 and 2006. It's mainly adult males that do it, Nevin reported this week at a British Ecological Society meeting in Glasgow, U.K. He says the evidence suggests that dominant males use tree marking to warn off or override the scent of competitors for both territory and females. It's an unusually thorough experiment, says Barrie Gilbert, who was Nevin's graduate adviser at Utah State University, Logan. But there are still a lot of unknowns—such as why bears choose the trees they do.

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