Another fascinating orca video made the rounds on the internet this week, only this time the whales were displaying some very strange behavior.  A few men were out for a boat ride in British Columbia‘s Discovery Islands, when they happened upon a family of orcas scratching their bellies on pebbles in some very shallow water near the shore.  The video shows the whales happily scraping the rocks, back and forth for nearly five minutes.  It almost looks like they’re trying to crawl on the bottom of the ocean!  Just watch:

So why were the orcas in need of such a belly rub? Carla Crossman, a research biologist at the Vancouver Aquarium, told CTV News Vancouver that scientists aren’t quite sure why this rare orca behavior occurs. “We don’t know why they’re doing it, but they’re very picky,” she said. “It’s very specific. This population of northern residents is one of the only populations in the world in which we see this behaviour.” This rubbing behavior has only been seen in the waters between Vancouver and Alaska, and only at a few beaches where the stones are smooth and about one inch in diameter.

Are they scratching an itch or exfoliating their bellies in some way?  Unlikely, according to Crossman. “It’s probably something social,” Crossman said. “Maybe kind of a ritualistic behaviour because they’re very specific in the beaches that they go to. They get really excited coming into these beaches. We see them kind of jumping up a little bit more, squealing, and making a lot of noise underwater.”

Click here to watch the full Vancouver CTV News report.  What do you think is the purpose of this mysterious orca behavior?  Let us know in the comments below!