Rough Side of the Tongue?
The spines on a cat’s tongue serve a variety of purposes
By Kim Campbell Thornton
Andrews McMeel Syndication
If you’ve ever been licked by a cat, you know the rough feel of the tongue, lined with rows of backward-facing barbs called papillae.
It used to be thought that papillae were in the form of a solid cone, but engineering researchers at Georgia Tech took a closer look and made a surprising discovery. Using 3D scanning with micro-computed tomography, the actual shape of the small spines was revealed to be not conical, but hollow. And that shape has a specific purpose.
“I liken them to ice-cream scoops,” says Alexis C. Noel, lead author of a paper published last December in the peer-reviewed scientific journal Proceedings of the National Academy of Sciences (PNAS). “They have this little U-shaped hollow from the tip down. We found that this cavity holds fluids really well.”
To test the action of the papillae, Noel and co-author David L. Hu introduced drops of food dye to the tip of the spine. “It sucked it up like a straw,” she says.
The scoop shape enables cats to use surface- tension forces to pull up water as they lap it, as well as to wick saliva deep into their fur, a way of cooling themselves.
“This shape makes much more sense, from a biomechanical standpoint,” says feline veterinary specialist Drew Weigner, DVM, who practices in Atlanta and is president-elect of the Winn Feline Foundation.
The investigation was inspired by Noel’s own cat, who was sitting on her one day while she watched TV.
“He decided to lick this microfiber blanket that he was on top of, and he got his tongue stuck in it,” she says. “I had to detangle him from the blanket, and it made me think. Everybody says cat tongues are kind of like sandpaper, but it really looks like the tongue is a lot more like Velcro.”
She and Hu hypothesized that when cats lick themselves, saliva — containing enzymes that break down fats and particulates — is distributed from the hollow spines, all the way down to the root of the hairs. They used high-speed videography to film three adult cats grooming themselves. During grooming, papillae become erect, increasing their contact area with fur. This contributes to saliva’s cooling effect.
Cats don’t have sweat glands over their bodies, except on their paws, so the thorough distribution of saliva helps to remove heat from the skin. Without papillae to push saliva deep into the fur, it would wet only the top layer of hairs.
The spines also help cats lick up oils, dirt, blood, feces and other contaminants. This not only keeps cats clean, but it also reduces odors that might otherwise expose their presence to predators.
Beyond domestic cats, Noel and Hu were able to examine the tongues of five other members of the feline family: bobcat, cougar, snow leopard, tiger and lion. What they found surprised them: Papillae are the same size and shape regardless of species.
That means the papillae of your tabby or tortoiseshell are just like those of a tiger or lion — except the big cats have more of them. Cats have about 300 papillae, while tigers have approximately 1,200.
“We thought that was strange because generally when you go from a small species to a large species, these things tend to scale, but these papillae didn’t,” Noel says.
On further investigation, they learned that no matter what the species, feline papillae are almost always long enough to penetrate fur and reach the skin. The exception is the Persian, with long, thick fur that’s impenetrable. “With these cats, the cat physically cannot push the tongue spine through the fur and reach the skin,” she says.