Are cat tongues clean?

Cat’s tongues are surprisingly complex — and better at cleaning than any brush we have

Cat’s scaly tongues are actually very, very good at cleaning fur. So good, in fact, that they could teach our doctors and engineers some tricks, a new study reports.

Feline owners out there will know that their pet’s tongue can be really scratchy — especially when they’re grooming. One team of researchers from Georgia Tech wanted to know why. Their research reveals how the rough tongues help cats clean their thick fur and cool down on hot days.

Rough around the middle

“Their tongue could help us apply fluids, or clean carpets, or apply medicine” to hairy areas on our body, says lead researcher Alexis Noel.

The secret behind the feline tongue’s roughness — and its superb cleaning ability — is a layer of tiny hooks that cover the surface. These hooks have groove- or scoop-like structures that help them drive saliva deep into the fur. They’re really effective at it, too. The team says these structures can help inspire new inventions for a wide range of application. Noel himself is already seeking a patent for a 3D-printed, tongue-inspired brush.

Cats, when not busy presenting us with dead presents, spend a lot of time grooming their fur; around a quarter of their waking hours are invested in personal hygiene, the team reports. Given how thick their fur can get, and how hard licking it clean seems to be, this isn’t really surprising at first glance. However, Noel’s curiosity was piqued when she witnessed her cat getting its tongue stuck in a fuzzy blanket. She wondered why her pet’s tongue is covered in those cone-like bumps. Luckily for us all, her lab has a background in animal-inspired engineering — so she set out to find the answer.

The team started by taking computerized tomography (CT) scans of cats’ tongues. This step revealed that the ‘cones’ are, in fact, hooks shaped much like a cat’s claws. They typically lie with their barbs pointing towards the neck (i.e. out of the way), until a certain tongue muscle springs into action. At that point, the spines spring straight up.

What really surprised the team, however, was that these spines (called papillae) contain hollow scoops. The researchers obtained preserved feline tongues (from zoos and taxidermists) to study — bobcats, cougars, snow leopards, lions, and tigers all share this trait, the team explains. Papillae were only slightly longer in lions than in housecats, although the tongues of larger felines hold many more such structures.

When dabbed with drops of food dye, these spines absorbed the liquid. Noel’s team estimates that a housecat’s papillae (roughly 300) hold saliva and release it when pressed against fur — and ensure that the animal can thoroughly clean its mane. Lab tests with a machine that the team constructed to mimic the strokes of a cat’s grooming showed that saliva from the tongue’s surface alone simply can’t penetrate as deep.

The team also measured cat fur. Our pets are usually quite fuzzy since their manes try to trap as much air as possible to insulate the animal. When compressed, however, the thickness of fur matches the length of these spines in many types of cat, the paper adds. One exception is Persian cats with their super-long fur that veterinarians caution must be brushed daily to avoid matting.

Finally, these spines aren’t just about staying clean — a thermal camera showed evaporating saliva cooled the cats as they groomed.

The paper “Cats use hollow papillae to wick saliva into fur” has been published in the journal Proceedings of the National Academy of Sciences.

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Why Does Your Cat’s Tongue Feel Like Sandpaper?

Cat anatomy is endlessly fascinating to me. Cats have some unique anatomical abilities that they share with no other species, and this is true for their tongue as well. That sandpaper sensation is caused by what is one of nature’s perfect designs: the cat’s tongue allows her to groom and to consume her prey.

Anatomy of the cat’s tongue

The cat’s tongue is covered with tiny, backward facing barbs called papillae. These papillae are made from keratin, the same substance that is found in human fingernails. These papillae account for the rough sensation you feel when your cat licks you. They’re designed to help the cat collect dirt, debris and and loose hair from her coat while grooming. They also help the cat pull meat off her prey’s bones.

Alexis Neol, a researcher at Georgia Tech, was so fascinated by her cat Murphy’s tongue that she decided to study cat tongues by creating a model that replicates the tiny barbs. She scanned a specimen of a cat tongue and 3D printed out the structure at 400 percent scale.

Staying clean is a matter of survival

The cat’s tongue is a more efficient grooming tool than any comb or brush. The individual spines are even shaped like miniature cat claws with a very sharp end,” Noel said. “They’re able to penetrate any sort of tangle or knot, and tease it apart.” Noel then put the artificial cat’s tongue through it’s paces inside a machine that drags the model across a patch of fake fur. To clean a traditional hair brush, you need to pluck the hairs out from between the bristles. Noel’s cat tongue model was much easier to clean: She simply ran her finger across the surface in the same direction as the spines. (Source: PBS Newshour)

Even though our house cats don’t have to use their tongues to pull meat off their prey, you’ll still notice them grooming thoroughly after each meal. Post meal grooming is a remnant of cats’ wild origin, where staying clean is a survival strategy: removing all traces of the scent of her meal will prevent other prey in the area to be alerted to the cat’s presence, and will also prevent potential predators from scenting the cat.

Grooming also helps the cat keep cool in hot weather.

Grooming for comfort

Grooming can also be a self-soothing mechanism. Some cats will resort to grooming when they’re nervous or anxious. Unfortunately, this behavior is sometimes taking to such an extreme that they will groom off all their fur on parts of their body. This excessive grooming is also called psychogenic alopecia (alopecia means hair loss). Cat guardians often don’t actually see the cat doing this, they just notice the bald patches. The cause of excessive grooming can be physical or behavioral.

The tongue helps cats drink

The tongue is also instrumental in helping cats drink. A few years ago, researches at MIT conducted a study into the physical dynamics of how cats drink. They studied high-speed video of cats to show how they flick the surface of water with the topside of the tip of their tongues. According to the researchers, the top surface of the cat’s tongue is the only surface to touch the liquid. Cats, unlike dogs, aren’t dipping their tongues into the liquid like ladles. Instead, the cat’s lapping mechanism is far more subtle and elegant. The smooth tip of the tongue barely brushes the surface of the liquid before the cat rapidly draws its tongue back up. As it does so, a column of liquid forms between the moving tongue and the liquid’s surface. The cat then closes its mouth, pinching off the top of the column for a nice drink, while keeping its chin dry.

Cats can’t taste sweets

Cats have fewer taste buds than humans, and they can’t taste sweets. For those cats that do like sweets, this habit has most likely been created by feeding species-inappropriate foods that are too high in carbohydrates and sugars.

Image Credit: Pixabay

This post was first published in 2017 and has been updated.

About the author

Ingrid King is an award-winning author, former veterinary hospital manager, and veterinary journalist who is passionate about cats.