Moles, Shrews Can Smell Prey While Underwater, Study Suggests

December 20, 2006

Get a whiff of this: Two small, semiaquatic mammals can use their sense of smell even when underwater, according to a new study.

The finding stems from high-speed video that shows a star-nosed mole rapidly blowing out bubbles of air and sucking them back in while foraging underwater.

The bizarre-looking rodent is already known as the world's fastest mammalian forager.

The mole has now displayed equal prowess as a lightning-fast underwater sniffer, blowing and inhaling air bubbles at a rate of five to ten times a second.

The bubbles make contact with a target, such as morsel of earthworm or fish, and apparently pick up the target's scent before being sucked back up the nose.

When you watch the video, "you're essentially seeing [the moles] sniffing underwater," said Kenneth Catania, a biologist at Vanderbilt University in Nashville, Tennessee.

"But that took a little while to dawn on me. You don't see what sniffing looks like in the air—it's invisible," he said. "Underwater it's visible."

Sniff Tests

On land, small mammals sniff by pushing air out and quickly inhaling, Catania said.

The air carries odors to special cells inside the nose that detect smells and send signals to the brain to help interpret the scent.

To determine if the moles were actually using air bubbles to transmit underwater smells, Catania trained the creatures to follow a scent trail that was underneath a submerged wire mesh.

The mesh prevented the moles from using the sensitive, fleshy appendages that ring their noses to feel the trail or the prey.

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