When marine biologist Sarah Fortune spotted bowhead whales rolling onto their backs in coastal waters near Canada’s Baffin Island several summers ago, she was baffled. The Ph.D. student at the University of British Columbia in Vancouver, Canada, knew that these arctic mammals rarely hang out in warm, shallow waters. And with few zooplankton around, they couldn’t have been in the bay to eat. So a few years later, Fortune and colleagues returned with a camera-equipped aerial drone to find out more. Their first clue was the whales’ unusual mottled skin and scratches along the length of their bodies. When the drone returned, they had their answer: Video recordings had captured the whales engaging in an impromptu exfoliation session, rubbing their chins, heads, backs, and sides against the large rocks. One bowhead was rubbing away for at least 8 minutes. Together with still images and a skin biopsy, the researchers conclude that these bowhead whales use rocks to rub away sloughing and molting skin, they report today in PLOS ONE. Though this is the first time scientists have seen this behavior in bowheads, other arctic whales—such as belugas—have been seen grooming themselves along abrasive bottom surfaces in Hudson Bay estuaries. One benefit to this annual skin cleansing? It might help the long-lived animals rid themselves of sun-damaged skin and parasites, the researchers say.