The New York Times online Science section published a short piece earlier this month by Joanna Klein about humming to periwinkles.
Joanna contacted me for some background on this story, which has a simple premise:
People who grew up in coastal New England know this trick: To coax a periwinkle snail out of its shell, hum to it.
This was news to me, but also sounded crazy enough that there might just be some truth to it. A dive into the scientific snail literature didn’t reveal any obvious mentions of humming to periwinkles to get them to emerge from their shells. I decided to give it a pseudo-scientific try with the local West Coast periwinkles (Littorina keenae). I grabbed a handful from the rocks and brought them into the lab where it was quiet. Half of the snails were put in a quiet room, and the other half I hummed at.
The snails I hummed at came out of their shells in less than a minute. But once I walked into the other room, where the remainder of the snails had been sitting quietly, I also found them all out of their shells and trying to roll over. Thus I had to play the role of the minor killjoy:
Dr. Miller tested it out for me with a West Coast relative of the common periwinkle. Results were inconclusive. “They will emerge after being picked up and carried around, without humming, so I’m not sure that humming is actually required,” he said.
As for why they come out of their shells, the article outlines it:
The snail’s goal in deciding when to emerge from its shell is to avoid being snatched up by predators or being swept deep into the ocean. So after a brief period of hiding after being disturbed by a crab, wave or human, it’s only a matter of time before it will come out to reorient itself, Dr. Miller said.
About 10 years ago myself and two other graduate students in the lab, Michael O’Donnell and Katharine Mach, did a little field experiment where we took Littorina keenae off the high shore rocks in Monterey and tossed them into the low intertidal, recreating what might happen if they were knocked off the rocks by a wave (read the paper here). When we went out to the shore on the following days, we found large numbers of our marked snails still crawling around, and over the course of several days a large proportion of them crawled back up the rock faces to reclaim their preferred spots high on the shore. Rolling around in the waves just increases the chances of ending up somewhere that the snail doesn’t want to be, such as inside a sea anemone’s stomach. So even without humming, we saw plenty of evidence that the periwinkles were quick to get their foot out and start crawling for home once they’d been pulled off their rocks.