The Speedy, Super-Sensitive Snouts Of Star-Nosed Moles | Connecticut Public Radio

The Speedy, Super-Sensitive Snouts Of Star-Nosed Moles

Jan 24, 2020

They might look like something out of science fiction, but star-nosed moles are real-life creatures that can be found along the East Coast, including in Connecticut. These small, furry mammals are a bit larger than a house mouse and live underground in wetlands, digging tunnels with their enormous claws.

But their most distinctive feature is their pink, star-shaped nose.

Ken Catania, Stevenson Professor of Biological Sciences at Vanderbilt University, has studied the neurobiology of the star-nosed mole’s strange snout for decades. He told Where We Live about the science behind these incredible creatures:

A star of fleshy appendages

“Of course, the elephant in the room is the star. So they have this totally weird nose, with 22 fleshy appendages that ring it ... [The star] is only about the size of your fingertip. It looks a bit like a starfish with extra rays, and these appendages ring the nostrils, right at the tip of the nose. So it’s basically like a miniature starfish attached to the tip of their snout.”

Credit Kenneth Catania

A nose like a tiny hand

“Most people would think nose, smell. But what you’d want to think about is the tip of your own nose is not how you’re smelling things; it’s the olfactory receptors inside your nasal cavity. It’s the same for star-nosed moles.

“These [appendages] are for somatosensation, or touch, in the same way our fingertips are very sensitive touch receptors. The star-nosed mole has 100,000 nerve fibers for touch concentrated in the size of your fingertip. That’s more than five times your entire hand, all in one fingertip. So that gives you a sense of how sensitive and acute and high-resolution their touch is.

“Another facet of this is to look at the mole’s brain organization. It has a huge area of the neocortex devoted to processing the receptors for touch.”

They’re wicked fast

“You need to use slow-motion video even to see how the star moves. What they’re doing is touching one place after another up to 13 times per second. As soon as they detect something that may be edible, they make a sudden movement -- in the same way you’d move your eyes if you saw something interesting -- to touch with that central portion of the star. 

“And then they can decide if that’s something they want to eat, eat it, and start searching for the next thing -- all in about a quarter of a second. They’re actually in the Guinness Book of World Records as the fastest foragers among mammals.”

Their super-sensitive snouts work a bit like our eyes

The star is an incredibly sensitive touch organ.
Credit Kenneth Catania

“The way they use [the star] for touch is really remarkable, because the side appendages are low-resolution, and the central appendages are what we call the ‘tactile fovea.’ So there’s a high-resolution central part, and a low-resolution part surrounding it.

“There are a lot of analogies with the way visual systems are put together, and also the way the auditory systems of bats are put together. They have the same sort of organization where particular frequencies are over-represented in a bat brain.

“The end result of putting together all those observations is you get a general rule for how evolution builds a really high-resolution sensory system. And that’s to make one area high-resolution, and the rest low-resolution, for scanning.”

Stranger than fiction

“When you look at unusual animals, and that’s sort of the specialty of my lab, they approach the kinds of things you see in science fiction. I actually think sometimes they outdo some of the things you see in science fiction. The speed of this animal, the weird face it’s got, the unusual teeth and what it’s able to do ... it’s something I could have never imagined ahead of time.

“There are no end of interesting mysteries, but sometimes the really extreme animals are not only the most fun to look at, but they reveal often a lot of general principles about biological systems: in the case of the star-nosed mole, the tactile fovea that’s organized like an eye. So I think these really interesting animals give you both the wow factor and the basic science factor.”