More than a Mustache

Whiskers!

We’ve all seen them on our pets’ faces and on squirrels and other rodents, rabbits, beavers, walruses, and some other mammals. Until recently, I didn’t give whiskers much thought. Then I learned they’re not just facial hair… and they’re not always on faces.

Mammals with long facial whiskers (humans aside) are equipped with what scientists call tactile hair or vibrissae. These special hairs are built to retrieve sensory information and pass it along to the brain. Some rodents and a few other animals move their vibrissae back and forth at high speed, using tiny muscles that move faster than other muscles in the body. This behavior, aptly called whisking, explains the hairs’ scientific name. It derives from the Latin vibrio, meaning to vibrate. As for function, picture the abundant, long whiskers of mice and rats on the run. They use them to locate exit holes and avoid obstacles. The three blind mice needed their vibrissae!

Maybe you noticed some unruly toe hairs on the raccoon in the photo above. Those are vibrissae, too.

Here’s another shot with a clearer view of the raccoon’s tactile toe hairs.

You might be wondering what triggered my interest in tactile toe hairs. One day, I noticed the amazing care with which that raccoon was grooming his feet. Back in May, he was snoozing daily in a broken tree trunk’s rotted nook that I call the balcony. He seemed to be out and about foraging each night. Come morning, he’d climb the trunk and settle into the balcony.

Mostly, he slept, waking up occasionally to swat a Tufted Titmouse that stopped by to pluck his hair—for nest material—as he slumbered. In late afternoon, he tended to rouse, and sometimes he preened. I noticed his hairy toes during one of those preening sessions.

Here’s a video of that particularly foot-centric grooming session.

Tactile toe hairs aside, he gave himself quite a foot massage. I wondered why—too much climbing and pouncing the night before?

It turns out he was taking care of his most valuable sensory assets.

It took just a few clicks to learn that a raccoon’s sense of touch is quite powerful. Its footpads have highly dense nerve endings that enable the animal to identify objects by touch alone. The ‘food washing’ we associate with raccoons isn’t a cleanliness habit. It’s a way to make those footpads more pliable and sensitive, perhaps to better judge the nature of the snack.

And back to the vibrissae. They extend beyond his toes, so he feels things before he touches them with his claws or pads. Raccoons are particularly sensitive to vibration, which helps them catch small prey like insects. Those tactile toe hairs help.

So, now you know that whiskers—or vibrissae, more broadly speaking—are more than just adorable mustaches.

Special note: I recently learned that a girls’ STEM club has been exploring my blog. So, girls: Check out these two source articles, one a deep dive into the biology of vibrissae, and the other about raccoons, with a terrific section about the animals’ senses.

Tony J. Prescott et al. (2011) “Vibrissal behavior and function.” Scholarpedia, 6(10):6642.

“Raccoon Natural History,” University of Wyoming Raccoon Project- Animal Behavior & Cognition Lab, accessed May 19, 2020.