Today I wanted to highlight one of my favorite sensory experts: the star-nosed mole. I wanted to focus on their astounding tactile and olfactory capabilities, but I also found out that they actually hold a Guinness World Record for being the world’s fastest eaters! I have a hunch that swimmers could give them a run for their money on the face-stuffing front, but that remains to be scientifically proven…
Starting off with olfactory, star-nosed moles are one of the only mammals that have developed a way to smell underwater. American water shrews are the only other mammal that has been documented exhibiting this behavior. The animals rapidly exhale and inhale air bubbles (approximately 10x/sec). They do not actually release their air bubbles, just suck them back in. It is kind of like if you blew a bubble with bubble gum, but, instead of blowing until it popped, you sucked the air back into your lungs. There is a picture shown in a Nature article, and this True Facts video has a little bit of sniffing footage right at the end of the video.
In regards to their tactile abilities, my favorite article was A Nose for Touch, which is a popular article written by a lead researcher on star-nosed mole research, Dr. Kenneth Catania. Dr. Catania also makes a cameo in this short clip by PBS about the star-nosed mole. The 22 fingerlike appendages that make up the “star nose” are called rays. The rays are adorned with dome-shaped Eimer’s organs, which in turn are innervated by over 100,000 neurons. The moles have more innervation going to their star nose, which is smaller than a human fingertip, than the total number of touch fibers found in the human hand! Another awesome fact that Dr. Catania and his team discovered is that the star structure is “mapped” on the mole’s brain (pictures in article). Whiskers on mice are also mapped in the brain in specific patterns that mirror how the whiskers are situated on the animal in real life. On that tangent, humans also have their body somewhat “mapped” in the brain. It is called a homunculus or “little man.” This article, Mouseunculus: How the Brain Draws a Little You, gives a great overview with helpful images, including cortical magnification images for Eastern moles, Naked mole rats, and Star-nosed moles! (shown below). The “cortical magnification” images basically depict what the brain thinks the body looks like depending on how much space is involved in the brain with processing information from that appendage. Thus, star-nosed moles have an extremely exaggerated representation of the star nose.
The Tangled Bank, 2nd ed., Carl Zimmer, Roberts & Company 2013 (see Mouseunculus article)
I find the idea of a homunculus super fascinating because I never really thought about how my brain perceives my body. Some food for thought! Even though the articles were not really about whiskers, I found them fascinating! I would love to see a publication on the sensory capacities of the whiskers on star-nosed moles. Some interesting/divergent findings probably exist because of the strong alternative sensory abilities of the star nose structure! As a final fun fact about moles, I leave you with some German. I learned the word for mole in German a few months ago, and I loved the imagery. Germans definitely have some of the best, most literal ways to describe things!
*Fun Fact: In German, a mole is called “der Maulwurf,” which literally means “the mouth throw.” I like the idea of describing moles as mouth throwers. 🙂