Anyone who owns a cat knows the furry beasts can spend an inordinate amount of time grooming themselves. Cats take that sandpaper tongue of theirs and just lick and lick and lick and lick for literally hours a day. But researchers are discovering more about what that tongue, with its hundreds of tiny, backward-facing spines called papillae, is doing.
In a new study published in the journal Proceedings of the National Academy of Sciences, researchers at Georgia Tech found that papillae are not cone-shaped and solid, as previously thought, but instead scoop-shaped and hollow.
"It allows the cat to store and hold saliva in these tiny little spines," says Alexis Noel, a researcher at Georgia Tech. She and her colleague David Hu used high-speed video and CT scans to observe how the papillae on a cat's tongue wicks saliva from its mouth onto its fur.
"When the cat goes to groom, the spines penetrate the fur and redistributes their cleansing saliva throughout all of their hairs," she says.
The team also studied different kinds of cat tongues and discovered that papillae are the exact same size and shape on every cat.
"Tigers actually have the exact same spines on their tongue as your house cat would, they just have a lot more of them," says Noel.
While all papillae may be created equal, a cat's ability to clean itself effectively is not — and it all has to do with fur.
For a cat to have optimal grooming, Noel says, the papillae need to penetrate through the fur layer and reach the skin so that the saliva can get to the root of the hairs.
"We found that for all of these different animals, from tigers, bobcat to snow leopard, the minimum fur height that you can compress to is always going to be less than the height of the papillae," she says. "Which makes us think that the papillae height and the papillae shape is actually optimal for a whole bunch of different types of fur."
Only one cat in their experiment was termed "un-groomable": the domestic Persian. The fluffier the cat, the harder it is for the cat to keep itself clean. Noel says this is why many long-haired cats get matted fur and have to be brushed daily.
"The cat is physically unable to get its little tongue spines all the way down to its skin," she says.
The researchers used this new information to 3D print a cat-tongue-inspired brush that is said to perform better when removing allergens from cat fur and is easier to clean. Noel says these findings can be used to make cleaning pets — and carpets — more efficient.
So what does this new research mean for cat owners the world over?
They're a fantastic species that has managed to optimize their tongues to be able to clean themselves better than any other animal, Noel says. "I guess, quantitatively speaking, you know your cat never really smells, but your dog does."