SCOTT DETROW, HOST:
Seal whiskers, turns out they're not just for show. They provide the animals with key intel on their surroundings. And new work suggests that maybe they help seals outmaneuver the evasive behavior of the fish they are hunting. Here's science reporter Ari Daniel.
ARI DANIEL, BYLINE: A harbor seal sports about a hundred whiskers.
YVONNE KRUGER: So these are sensory hairs in the facial region. And with these whiskers, they can sense the water movements that are generated by fish.
DANIEL: It's as if the fish are leaving behind underwater trails, says Yvonne Kruger, a biologist at the University of Rostock in Germany. Trails that a seal can follow to find the fish and gobble them up.
KRUGER: You can't see it, but you can sense it with the whiskers.
DANIEL: Seals can use their whiskers to pull all sorts of information out of the water. They can determine the direction in which something has traveled, and lab studies suggest seals might even distinguish between the movements of different types of fish. But fish don't just let themselves be eaten. The rainbow trout, for instance, a favorite food of the harbor seal, has an escape strategy.
KRUGER: Rainbow trout are able to camouflage their swimming direction by bending into a C shape. And then they swim away in a different direction they have been swimming before.
DANIEL: This new posture causes the trout to spin off two vortex rings in opposite directions, kind of like smoke rings made out of water. And only one of those rings, the slightly smaller one, moves in the direction the fish is swimming in, potentially confusing a harbor seal in pursuit.
KRUGER: So I wanted to know if a harbor seal can read that camouflage and still follow the fish.
DANIEL: Kruger thought that if a seal could differentiate between the sizes of the vortex rings, it'd know the correct one to chase. To test her idea, she worked with an adult harbor seal living at a marine science center in Germany...
(SOUNDBITE OF SEAL ROARING)
DANIEL: ...Named Filou. Here he is roaring and slapping his side with his flipper.
(SOUNDBITE OF SEAL SLAPPING)
KRUGER: We have a very strong bond. So Filou actually likes to do everything correct. He likes learning new things. If he has one mistake, he gets frustrated. Yeah, he's a nerd.
DANIEL: In the experiment, Filou had to learn to select the bigger of two vortex rings generated artificially underwater. Kruger spent almost two years training him, but he finally got it and was able to distinguish between the rings, even when the size difference was less than the width of your thumb and far less than what they'd need to discern in the wild.
KRUGER: Which tells me that Filou would still be able to follow the correct direction to successfully hunt and prey on the rainbow trout.
DANIEL: It's just one animal, but Kruger and her colleagues say it's likely true of harbor seals more generally. The research is published in the Journal of Experimental Biology.
ROBYN GRANT: I would've loved to have some information about the precise movements of the whiskers, but this is a great start to tell us what they're capable of doing.
DANIEL: Robyn Grant is a sensory biologist at Manchester Metropolitan University who wasn't involved in the study. She says it's worth understanding how an animal like a harbor seal senses its surroundings to know how it might be affected by changes to its environment, including extreme weather events.
GRANT: You can imagine that that can mask some of these critical stimuli that the seals would like to pick up.
DANIEL: Plus, Grant says these findings may inspire sensors that could help aquatic robots navigate their surroundings for underwater archaeology or biological surveys.
For NPR News, I'm Ari Daniel.
(SOUNDBITE OF AMIE BLU SONG, "EVERYTHING ABOUT HER") Transcript provided by NPR, Copyright NPR.
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