One day, research engineer Alexis Noel’s cat, Murphy, was blithely licking away—as cats do—when he got his tongue stuck on a microfiber blanket. The cat licked himself free, but Noel was fascinated by the process, and wondered why the feline’s tongue was so good at untangling knots and smoothing out fur. But when she looked at the literature, she realized engineers had more or less ignored the biomechanics of the miraculous pink tongue brush.
That’s why, in a new study in the journal PNAS, Noel and her colleagues sought to untangle the mysteries of cat tongues. A previous study reported that domestic cat tongues are covered in cone-shaped bumps that were used as brush bristles, whereas the Noel’s team found that the protrusions are actually claw-shaped hooks with hollow U-shaped tips.
The bristles lie flat and rear facing when at rest, but when it’s time to get their groom on, the cat pops the spines straight up. The scoops on the bristles’ tips pick up saliva using water tension and distribute the saliva as the cat licks itself. In fact, when the team dripped food dye on the spines, or papillae, they were able to wick up some of the liquid color.
The papillae aren’t just found on domestic cat tongues either. The team was also able to examine the tongues of a bobcat, cougar, snow leopard, tiger and lion. They created 3D scans of the lickers, finding that they all have papillae of similar size and shape, though the big cat tongues have many more spikes on them. Though the papillae are pretty short, the researchers found that even for the big cats they were long enough to comb out fur once. The only exception was the Persian cat, whose tongue papillae just aren’t long enough to deal with their flowing luxurious coats.
It turns out technique matters, too. The team also recorded cats grooming themselves using high-speed video and found that the little tongue spikes rotate when they encounter knots, which allows the cat to work out the tangles and snarls.
Over the course of an entire day of licking, a cat spreads about one fifth of a cup of water across their fur, reports Carrie Arnold at National Geographic. So, why all the grooming? Besides making the kitties look fabulous, thermal imaging showed that keeping their fur well-groomed also created a 30 degree temperature difference between the skin and outer fur as all that saliva evaporated, keeping the cats—which only sweat through their foot pads—cool.
All that awesome engineering inside the cat’s mouth inspired the team to create their own version. Using a 3D printer they created a small tongue-inspired grooming brush (TIGR) that mimics the action of the cat papillae. Frankie Schembri at Science reports that the team believes the brush could be a hit with pet lovers since it mimics the way cats groom. It is could also be used to get medicine directly to the cat’s skin.
Even better, the brush should be able to scrape cat fur off the couch better than your vacuum cleaner.