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Underwater Sniffs

Have you ever tried smelling underwater? Probably not the best idea, since as humans we would drown, but that's not the case for the star-nosed mole.

Nest of baby star-nosed moles

Photo: Hillbraith (flickr)

Star-nosed moles like these in Ontario can smell food underwater by breathing in air bubbles

Have you ever tried smelling underwater? Probably not the best idea, since as humans we would drown, but that’s not the case for the star-nosed mole.

It seems that some land-mammals that sometimes forage for food underwater, such as star-nosed moles and water shrews, may have the ability to sniff out food sources while submerged.

While underwater, the moles exhale air bubbles onto objects they want to smell. Then they quickly re-inhale the bubbles to carry the odor back through the nose.

Kenneth Catania, a biologist at Vanderbilt University discovered the underwater sniffs when he made high-speed video recordings of swimming star-nosed moles and water shrews. The videos showed the moles and shrews were continuously blowing and re-inhaling air bubbles from their noses when hunting for food.

He tested the moles and shrews to see if they could follow a scent trail to find a food source. He dragged an earthworm or fish across a piece of Plexiglas, and then placed the odoriferous plastic at the bottom of a water-filled tank. He found that both the water shrews and star-nosed moles could accurately follow the invisible scent- trails using underwater sniffing in over eighty-percent of trials.

The surprising finding in the moles and shrews has scientists rethinking old assumptions that smell is a sense not used underwater. Perhaps we’ll find that other aquatic mammals are underwater sniffers too!

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