Seals, unlike other mammals, have long and curly whiskers that bulge at the end. Is there any particular reason for this feature? “This shape enhances their ability to detect flows created by fish,” says Heather Beem, author of a study on seal whiskers soon to be published in the Journal of Fluid Mechanics.

“Whiskers are likely to have many functions, from texture sensing to shape discrimination,” says Mitra Hartmann, a Northwestern University engineer who studies whiskers but was not involved in the new research.

Other animals, such as rats, use their smooth whiskers to know surfaces. Rough surfaces provide different vibrations as compared to smooth ones. For harbour seals, we see the same technique at play to some extent. A far off fish can cause tiny ripples while swimming by. The long whiskers have astonishingly shown an enormous amount of sensitivity to this movement. Thus, the whiskers enable the cunning predator to track its underwater prey from hundreds of feet away.

In a study performed to confirm this hypothesis, German scientists blindfolded seals and forced them to wear headphones. The result was that they could still pick up the lingering trail of a fish, using their whiskers, half a minute after it had passed.

Beem performed other experiments including building a plastic replica of whiskers and testing their response to ripples made in the water by an artificial fish swimming ahead. Smooth whiskers, she reckons, would flap madly as fluid flowing over a smooth object forms whirlpools whose vortices would tug on a smooth hair, making it wiggle.

In case of wavy whiskers though, “The waviness breaks up the water flowing over it,” says Beem. As other questions remains such as whether the effect of ripples would be affected due to the big head of the seal, she looks forward to future applications of the plastic whiskers. These would include enhancing the ability of aquatic robots involved in monitoring migration to sense fish.

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Author:Technology Blog