Artificial whiskers allowed scientists to study harbor seals' incredible ability to detect prey, and the findings could be used to improve the technology of underwater vehicles.
Even when blindfolded, harbor seals can follow the path of an object that swam by 30 seconds earlier, MIT reported. A large-scale model of a harbor seal's whiskers revealed this feat is possible because of a key mechanism.
Seal whiskers sense the surrounding environment in two ways: they remain still in respond to a seal's own movement through the water; and they oscillate in a "slaloming" motion in response to the turbulence left by a moving object. The recent experiments demonstrated that when the artificial whiskers encountered a wake left by a passing object, they started to vibrate at the same frequency as the wake's vortices. This slaloming allows the whiskers to extract energy from the wake, and tells the seal the object's path, size, and shape. The whiskers also have a unique "wavy" shape that is believed to contribute to their ability to sense objects in the water and block out disturbances caused by the seal's own movement. The morphology of the whiskers created much weaker vortices that allowed the whiskers to move silently through the water, causing little vibration. The researchers compared the process to having the ability to stick one's head out of the window of a moving car to achieve a "quieting effect."
"The geometry of the whisker allows for this phenomenon of being able to move very silently through the water if the water's calm, and extract energy from the fish's wake in order to vibrate a lot," said Heather Beem, whose PhD thesis formed the basis of the study. "Now we have an idea of how it's possible that seals can find fish that they can't see."
The artificial whiskers provide key insights into seal behavior, but could also be used to help underwater vehicles track schools of fish and even sources of pollution.
The findings were published in a recent edition of the Journal of Fluid Mechanics.