Bears may self-medicate against ticks by rubbing against trees

Brown bears often scratch their backs on trees, leaving behind chemical signals to other bears. Now, it seems the act also helps protect them from ticks

By Jake Buehler

Bears that rear up to scratch their backs against a tree trunk smear themselves with pungent resin, possibly keeping bloodsucking parasites at bay.

Brown bears (Ursus arctos) regularly scrape their necks, chests and backs against trees. The behaviour is often thought of as chemical communication with other bears, through the animals depositing their own odours or picking up a coating of aromatic resin. Bears will also gravitate towards smellier options for tree-rubbing, such as creosote-treated power poles.

But since many odoriferous plant oils and other substances have anti-fungal …