For decades bear biologists have known that bears engage in a delightful ramble variously dubbed “sumo strutting,” “cowboy walking” or, simply, the “bear dance.” Many researchers have guessed at the reason, but a recent study finally offers solid clues.

As they walk, the bears vigorously twist their feet into the ground. Sometimes they step into footprints left behind by other bears after giving the prints a good sniff. Some have referred to these collective tracks as bear highways because they become well traveled over time.

“Everyone suspected that there was something in [the footprints],” says Agnieszka Sergiel, a biologist at the Polish Academy of Sciences' Institute of Nature Conservation and a co-author of the study, which was published recently in Scientific Reports. “But no one really investigated.” She and her colleagues wondered whether the bears deposit their scent through glands on their paws as a means of communication.

Sergiel's team examined a pair of brown bears and determined that the animals' paws contain sweat glands, suggesting that the prints leave behind a scent. The researchers also identified 26 different volatile compounds—six of them unique to males—in paw sweat, indicating that bears may use aroma to determine the sex of previous ursine travelers.

Sergiel says the bear footprints are akin to mailboxes, although the messages they send remain a mystery.