WASHINGTON The whiskers that give seals their winning expressions are more than decoration -- they let the animals track prey in even the murkiest water, Reuters quoted researchers as saying on Thursday.

Because a harbor seal's whiskers have between 1,000 and 1,600 nerve fibers per hair, they are possibly the most sensitive whiskers in the animal kingdom, said researcher Guido Dehnhardt of Germany's Ruhr-Universitat Bochum.

Dehnhardt and his colleagues enlisted Mike and Henry, two harbor seals from the Cologne Zoo in Germany, to help show that seals can use these highly attuned whiskers to track a water disturbance even in very clouded conditions and when the object that disrupted the water is long gone, at distances that could range up to 591 feet (180 meters).

Dolphins use a sort of sonar called echolocation to find their prey, pinpointing locations by measuring how long it takes a sound wave to bounce off an undersea object. But researchers had been unable to find evidence that pinnipeds, the group that includes seals, had anything similar.

A study in the current issue of the journal ***Science*** tells how a blindfolded Henry -- after being trained to follow a miniature submarine without any sensory restrictions -- was put in murky water with headphones on to mask sound. Then, after turning off the motor, researchers removed the headphones and released the seal so it could try and find the little sub.

Not only did Henry track the sub 256 out of 326 times, he actually followed the exact path it had tracked 80 percent of the time.

The seals were able to track the submarine from as far away as 131 feet (40 meters).

The sub's water disturbance trail lasts 30 seconds but fish leave trails that can last three to five minutes, the time it takes a goldfish to swim 164 feet (50 meters), Dehnhardt said.

"Fish trails are much more stable than the submarine's trail. The submarine's trail has several components which are similar to fish trails but they are not that stable so they disappear in 30 seconds," he said in a telephone interview.

"But these long-lasting fish trails, they should be usable by a seal to detect. For example a herring, if the herring is about 328 to 591 feet (100 to 180 meters) away or even more, it depends on the size and the swimming style of the fish," Dehnhardt said.

When their whiskers were covered with a stocking mask, the seals failed to find the sub.

Now Dehnhardt and his colleagues are planning to take things one step closer to nature, using real fish which they will train to swim from one point to another in a tank. When the fish is safely in a little chamber at the other side of the tank, they will let the seal try to follow.