Blindfold a harbor seal, clap headphones on its ears, and the keen hunter will still be able to track a distant fish, using its whiskers to detect the ripples made by its prey. Now, scientists have figured out the secret to the whiskers’ remarkable sensitivity: their wavy shape. To simulate a whisker on a swimming seal, the researchers made a model hair and dragged it through a tank of water. A simple cylindrical whisker would have flopped around violently, much like the antenna on the hood of car does in the wind. But the curvy whisker model with its ellipse-shaped cross section barely wiggled, suggesting that the whiskers of a seal tearing through water at top speed would stay relatively still, the researchers report this month in a paper posted to the arXiv preprint server. Only when a second object was introduced into a tank, a simulated fish, did the model begin to twitch significantly. It vibrated in sync with swirls of water shed by the fake prey, sliding like a skier on a slalom course from vortex to vortex. Able to efficiently harness the energy of the whirlpools, the shapely whisker was set in motion even by slow-moving eddies generated by a faraway “fish.”

(Linked photo credit: T.C. Murphy et al., PLOS ONE 8, 7 [2013])