Fur is compressed when a cat grooms itself. The barbs on a cat’s tongue are just the right length to comb through the pressed-down fur. (AP)

Fur is compressed when a cat grooms itself. The barbs on a cat’s tongue are just the right length to comb through the pressed-down fur. (AP)

A close-up photo shows the surface of a cat's tongue with its papillae angled back. (AP)

A close-up photo shows the surface of a cat's tongue with its papillae angled back. (AP)

Compare the tongue barbs (papillae) of felines seen in CT scans. (AP)

Compare the tongue barbs (papillae) of felines seen in CT scans. (AP)

A close-up photo of a tiger's tongue (AP)

A close-up photo of a tiger's tongue (AP)

Cat Tongue Tech

Posted: March 4, 2019

You know cats have super scratchy tongues. You can hear the scratching while a cat gives itself a bath! Now scientists use high-tech scans and some other tricks to answer a question. How do those sandpapery tongues help cats get clean and stay cool?

Here’s the secret: Tiny hooks spring up on the tongue—with scoops built in to carry saliva deep into all that fur! The find could lead to inventions for pets and people. Researchers say cat tongue tech could help us clean carpets or apply medicine to hairy skin. One researcher, Alexis Noel, is trying to get a patent for a 3D-printed brush that acts like a cat tongue

Cats are fastidious. They spend up to a quarter of the time they’re awake grooming. That would be like you taking a three-hour bath every day! Ms. Noel first grew interested in cat tongues when her cat, Murphy, got his tongue stuck in a fuzzy blanket. Before now, scientists thought cat tongues were studded with tiny, cone-shaped bumps. Ms. Noel disagreed. Scans of cat tongues showed they’re not covered in solid cones but in claw-shaped hooks. The hooks lie flat. They face the back of a cat’s throat . . . until the tongue muscle twitches. Then the little spines spring straight up.

But Ms. Noel got a surprise. Those spines contain hollow scoops! Ms. Noel borrowed preserved cat tongues from zoos and taxidermists. (Taxidermists preserve and stuff dead animals.) She found that bobcats, cougars, snow leopards, and even lions and tigers have the same kinds of spiny tongue scoops.

Ms. Noel touched the tips of the spines (called papillae) with drops of food dye. The spines sucked the dye up. A housecat has 300 papillae on its tongue. They hold a little bit of saliva that releases when the tongue presses on fur. Ms. Noel could tell the spines were designed for deep cleaning. Papillae on lions were just slightly longer than the ones on housecats. (But cats with bigger tongues have hundreds more papillae than smaller-tongued cats.)

Next, Ms. Noel measured cat fur. Cat fur holds lots of air to insulate a cat. It keeps felines warm the same way feather-stuffed jackets keep people warm. Sure enough, if you compress that fur, the distance to the skin matches the length of the tongue’s spine. God made the cat’s tongue spines exactly the right length to clean its fur! A machine mimicked the strokes of a cat’s grooming. It showed that a cat washing itself just with saliva wouldn’t get as clean. And a thermal camera showed that as cats groom, evaporating saliva acts like an air conditioner!