The Star-Nosed Mole Has the World’s Most Sophisticated Sniffer

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Close-up of star-nosed mole's face and front paws.

The star-nosed mole’s distinctive nose features 22 highly sensitive feelers.

© K. Catania


The eyes of the star-nosed don’t work very well. In fact, like most moles, it’s practically blind. But since it lives in near-complete darkness, burrowing beneath moist soil near ponds and streams in wetlands across southeastern Canada and the eastern United States, this creature doesn’t need sharp vision. It has something that works even better: one of the most specialized noses in the world.

 

Night ‘Vision’

The mole’s extraordinary nose is ringed with 22 finger-like tentacles, each measuring no more than 0.25 to 0.5 inches long, which encircle its nostrils like two side-by-side starbursts. But if you look closely at each of its waving feelers—under a microscope—you’ll notice that they’re covered in approximately 25,000 papillae that look a lot like tiny taste buds. These sensory receptors are known as Eimer’s organs, so-named for the German scientist who discovered them in 1871. The receptors help the mole to detect details about its environment when it presses each of its 22 “rays” rapidly against the soil.

 

Nose on the Brain

In a 2011 study in PLoS One, neuroscientist Kenneth Catania of Vanderbilt University revealed that not only was the mole’s nose capable of processing sensory information but that its star shape was actually mirrored in the structure of the animal’s brain as well. As it turns out, a system of 100,000 neural links from each individual ray correspond to a different section of the brainstem and neocortex. Every time the mole’s nose reaches out into the wet, swampy dirt (touching something up to 10 times per second to identify it) a comprehensive imprint of its immediate surroundings is sent to its brain.

 

Air bubbles form on the finger-like tentacles of a star-nosed mole's nose.

The mole can smell underwater by exhaling and then inhaling bubbles with trace amounts of odor molecules.

© K. Catania


Scent for Swimming

Catania has also found, in a study published in 2006 in the journal Nature, that star-nosed moles are one of only two mammals, along with a species of water shrew, which have the ability to smell underwater. By rapidly exhaling and inhaling bubbles to pick up trace amounts of odor molecules in the water, the star-nosed mole can sniff out crayfish, insects, frogs, and fish for a meal during its dive.

The star-nosed mole’s quick feelers also helped the species earn a place in the Guinness Book of World Records as the fastest eater of any mammal, clocking in at 120 milliseconds for its quickest find-and-gulp.

 

Learn more about the senses of different species in our new exhibition Our Senses: An Immersive Environment.