'Wonder Whiskers' Help Seals Find Food

With their endearing gaze and long, versatile whiskers, harbor seals Henry and Nick became instant celebrities on 6 July, appearing in newspapers around the world, after being immortalized in the journal, Science. News coverage explained how Henry and Nick are helping scientists gain new insights into the underwater foraging strategies of seals.

Even blind-folded, it seems, the seals can quickly locate a toy submarine as it zips through an experimental pool. But, try covering their whiskers with a mask, and the seals won't be able to track the toy in murky water.

This finding, reported by Guido Dehnhardt and colleagues at the Ruhr University of Bochum, Germany, reveals how seals pinpoint their next meal, by using their super-sensitive whiskers to detect the water trails created by swimming prey. Scientists had long suspected that seals use their whiskers to locate easily accessible snacks, within their immediate vicinity. But, the Science study shows that the animals wonder whiskers also serve as long-range sensors, allowing them to track food from a distance.

Its a first demonstration of the ability of an animal to follow turbulent trails in the water, said Andrew Sugden, a Supervisory Senior Editor for Science, based in the journals international headquarters office in Cambridge, U.K. The intriguing question is whether seals use this ability to catch prey, or whether they use it to locate each other, or both..

Dolphins use a sonar-like system called echolocation to forage in dark, murky waters, Dehnhardt notes in his paper. But, seals, also known as pinnipeds, apparently lack this sensory ability.

To find out more about seals food-finding strategies, scientists first trained Henry to locate the submarine in a pool of murky water, without any sensory restrictions. Then, they placed a blindfold and headphones on the seal, and positioned him with his head above water. The submarine was started under water, and stopped a few seconds later. When researchers removed the headphones, that was Henrys signal to begin the search. The researchers conducted the second experiment in clear water, with Nick demonstrating his dive-and-forage skills.

A frame-by-frame video analysis shows Henry clung to the murky water trail nearly 80 percent of the time, overall. Moreover, the seal:

Located the submarine in 256 out of 326 total attempts; Found the submarine 24 out of 30 times when it wasn't allowed to begin searching immediately; Found the submarine 26 out of 30 times when researchers altered its course mimicking a fish; and Failed 30 out of 30 attempts when his whiskers were covered with a stocking mask.

As a next step, Dehnhardt said, researchers will need to know more about the seals behavior in authentic conditions, in the wild, in order to figure out the greatest distance at which a seal can detect a fish. The research will continue with trained animals in the ocean, they said.