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Animalia

A cat's sandpapery tongue is actually a magical detangling hairbrush

By Karin Brulliard

November 29, 2016 at 12:14 PM

This cat isn’t just cleaning its paw. It is spreading oils, improving its circulation, regulating its body temperature and detangling its fur. (iStock)

Cats, depending on your point of view, are cute or aloof, predatory or lazy. What's indisputable is that they are well-honed little machines.

Take their ability to flip over while falling, which makes them appear to violate the rules of physics. Or their way of balancing gravity and inertia to keep their whiskers and chins dry while lapping up beverages, unlike their sloppy canine housemates. Cats' ears can move in multiple directions, and they can hear at two octaves higher than people. Their paws are perfectly moistened to keep their movement quiet, helping them stalk their prey.

Related: [Scientists just can’t stop studying falling cats]

Now researchers at Georgia Tech have unmasked yet another example of cats' efficient anatomy: Their rough pink tongues are actually hairbrushes far better at detangling — and much easier to clean — than the hair tools for humans that are available at your local drugstore. This is no small detail for cats, who can spend half of their awake hours grooming, and not just out of vanity. Those licks remove fleas and dirt, spread body oils and improve circulation.

Despite common wisdom, the tongue that carries this out is not like sandpaper at all, according to the researchers, who created a 3D-printed cat tongue model to prove their point. Cat tongues are covered in tiny, backward-facing spines that are shaped like claws and made of keratin, the same material fingernails are made of. In a "single grooming sweep," the researchers wrote, a cat tongue moves in four directions, helping the tongue essentially act as a flexible comb that adapts to the knots it encounters.

A cat’s tongue is covered in little Velcro-like hooks. (iStock)
A close-up of a cat tongue’s claw-like spines. (Courtesy of Alexis Noel)

"When the tongue glides over fur, the hooks are able to lock onto tangles and snags," said lead author Alexis Noel, a PhD candidate in mechanical engineering who presented her research at a physics conference this month. "As the snags pull on the hook, the hook rotates, slowly teasing the knot apart. Much like claws, the front of the spine is curved and hook-like. So when it encounters a tangle, it is able to maintain contact, unlike a standard hairbrush bristle, which would bend and let the tangle slide off the top."

Related: [The spooky history of how cats bewitched us]

And as shown by the 3D-printed cat tongue — made at a scale of 400 times the size of an actual cat tongue — the flexible spines lie flat when they're not in lick mode, enabling collected fur to slide right off (and be swallowed and balled in the gut for handy hacking on the carpet at a later date). Most hairbrushes, in contrast, have spines that stick straight out and gather hair in a yucky mat that requires effort to extract. Check out the difference in this video:

Watch more!
Researchers are figuring out why cat's tongues are so good at cleaning. (Gillian Brockell/The Washington Post)

Noel, who describes her focus of study as "adhesion with soft, squishy materials," said she first became intrigued by the cat tongue while watching her family cat, 3-year-old Murphy, lick a blanket and promptly get stuck. He soon freed himself by pushing his tongue into the blanket, which Noel now knows means he was unhooking his tongue spines from the blanket loops. Here's a video of another cat trapped by a blanket:

If you've made it this far, you may be wondering why cat grooming mechanics matter. There are two big reasons: First, it might add insight to the field of soft robotics, which, among other things, is about making robots that can move through small spaces for search-and-rescue missions or surgeries. Second, it might help make a better brush that, Noel said, could herald "new ways to clean deeply embedded dirt in your carpet to wound cleaning advances in the medical field."

Even better? It could bring a cat-tongue-style brush to a hair salon near you. Noel and colleagues are applying to patent their 3D tongue, and they're planning to talk about possible uses with professionals in various fields — including the beauty industry.

Read more:

Your dog is watching you very carefully and remembers what you do

First a polar bear petted a dog. Then a polar bear did what polar bears do: Ate a dog.

Two moose locked antlers in a fight, then froze together in a stream

Should dogs be guinea pigs in government research? A bipartisan group says no.


Karin Brulliard is a national reporter who runs the Animalia blog. Previously, she was a foreign correspondent and a local reporter.

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