1/2/2007

New York Newsday

Hey, what's that underwater smell?

You'd know if you were a star-nosed mole. Chalk up another improbable feat for the semi-aquatic mammal with the unforgettable schnozz, as a new study suggests the mole can rapidly exhale and inhale air bubbles to trap submerged odor molecules.

Most scientists had assumed the scent-tracking snouts of mammals would prove useless underwater since air is required to usher odor molecules to the sensory cells within nostrils. For many whales, in fact, research suggests the ability to sniff out odors has faded away.

But Kenneth Catania, an assistant professor of biology at Vanderbilt University in Nashville, became curious when he saw one of his star-nosed subjects blowing ample bubbles while swimming underwater.

"After watching the behavior for a while, it was kind of one of those light bulb moments," he said. "I looked at this behavior and thought, 'Well, it probably has a function.'"

In high-speed video recordings, he discovered that the mole - a rarely-seen Long Island native - can sidestep the predicament of other mammals that venture into water by exhaling and inhaling air bubbles up to 10 times per second. The rapid exchange, he writes in a recent issue of the journal Nature, seems to mirror the terrestrial sniffing behavior of rats.

"The only reason that I was slow in coming to that conclusion is that we don't normally get to see what a sniff looks like," Catania said. "But if we could, it would look exactly like what these animals are doing underwater."

When he blocked the moles' ability to use their highly sensitive fleshy appendages as feelers, the mammals still efficiently followed underwater fish and earthworm scent trails by blowing out and re-inhaling the air bubbles. Their command performance was halted, however, if the air bubbles were blocked with a fine mesh grid or if the trail proved scentless.