The common mole can smell in stereo. Seeing and hearing in stereo is common amongst many mammals, including humans, and allows an animal to zero in on and locate the source of a sound or sight, which is often vital for finding prey.
A new study published in Nature Communications, "Stereo and Serial Sniffing Guide Navigation to an Odor Source in Mammals," has found that moles have the ability to detect the location of a smell. "I came at this as a skeptic. I thought the moles' nostrils were too close together to effectively detect odor gradients," said researcher Kenneth Catania, the Stevenson Professor of Biological Sciences at Vanderbilt University.
Catania first started studying the common mole 10 years ago, while conducting research on the star-nosed mole, a bizarre creature with a set of tentacles surrounding its nose that detect food as it burrows. The neuroscientist first tested the common mole's smelling capabilities as a comparison to its star-nosed cousin. "I expected the common mole, which is virtually blind and doesn't have a very good sense of touch, to be a lot worse than the star-nosed mole" he told Phys Org. "So I was quite surprised when they turned out to be very good at locating prey."
Last year, Catania conducted an experiment to test the common mole's surprisingly effective sense of smell. He created a semicircle-shaped enclosure with food wells spaced around the 180 degree curve and placed the mole's entrance at the center. The chamber was also temporarily sealed so Catania could detect the mole's sniffing from changes in air pressure. The moles were startlingly accurate. "It was amazing. They found the food in less than five seconds and went directly to the right food well almost every time," he said. "They have a hyper-senstive sense of smell."
When the moles enterted the chamber, they scanned the area by moving their noses back and forth, and then moved in a straight line to the food, seemingly zeroing in on the source of the scent. This suggested "stereo sniffing," an ability not seen in untrained animals.
Catania investigated the moles' stereo smelling by blocking one of the moles' nostrils with a small plastic tube. When a mole's left nostril was blocked, it veered off to the right. When its right nostril was blocked, it veered to the right, taking a significantly longer time to find the food. Catania then placed the moles in a chamber where the food was directly across from the entrance. The moles with a blocked nostril veered away from the food, and those with use both nostril sniffed from the left side and the left nostril from the right), the moles frequently couldn't locate the food at all.
These findings are similar to a 1979 study done at the California Institute of Technology performed with owls. When one of the owls' ears was blocked, it frequently misjudged the location of the source of the sound.
Moles not be the only animal that uses stereo smelling. "The fact that moles use stereo odor cues to locate food suggests other mammals that rely heavily on their sense of smell, like dogs and pigs, might also have this ability," said Catania.
