Moles Can Smell in Stereo

When we see or hear something, our brains present us with one image or one sound. But each ear or eye takes in different information. Need proof? Try this, Scientific American suggests:

Hold two fingers up, one in front of the other. Now, while fixating on the closer finger, alternately open and close each eye. You’ll notice that the farther the far finger is from you (don’t move the near finger), the greater the lateral shift in its position as you open and close each eye. On the retinas, this difference in line-of-sight shift manifests itself as disparity between the left and right eye images.

But we don’t process our fingers as two separate images or sounds coming from either eye and ear. Rather, our brains assimilate that information into one coherent picture or noise. This capability is called seeing or hearing in stereo. Moles, it turns out, can also smell in stereo, new research from Vanderbilt University shows.

To locate prey, researchers discovered, common moles rely upon stereo sniffing. Moles’ nostrils are quite close together, so many researchers assumed stereo capabilities would not apply to their sense of smell. To find out for sure, the Vanderbilt team built a mole arena with different foods spaced around a 180-degree circle. The mole entered the buffet at the center, which was sealed so the researchers could detect minute changes in air pressure each time the mole sniffed towards one of the offerings of earthworms contained in different wells around the perimeter.

The naturally blind moles located their wormy prey in less then five seconds, heading to the correct worm bucket nearly every time. After watching this take place for a while, the researchers noticed that the moles tended to first move its nose back and forth as it sniffed, then zero in on the food source and waddle directly towards it.

To tease out these dynamics, the team blocked one of the moles’ nostrils. Under these new circumstances, the moles’ detection abilities wavered slightly, and they veered to the right when their left nostril was blocked, and to the left when their right nostril was blocked. They still found the food, it just took them longer to work out the correct path.

In a final example of experimental creativity, the researchers inserted small plastic tubes into both of the moles’ nostrils and crossed them so the right nostril sniffed air to the left and vice versus. When this happened, the animals wavered back and forth and often didn’t succeed in finding the food at all. Imagine you right eye seeing images from the left and your left eye seeing images from the right, and you can understand why the moles were confused.

The researchers concluded that their studies provide evidence that moles do indeed smell in stereo, using their two nostrils to paint a full olfactory picture of the world around them. Whether other mammals, such as dogs and pigs, also share this ability remains to be sniffed out.

Here, you can see the hungry and sometimes befuddled moles going about their business.

More from Smithsonian.com:

What Does Home Smell Like?
We Can Only Process Thirty Smells at One Time

Rachel Nuwer | | READ MORE

Rachel Nuwer is a freelance science writer based in Brooklyn.