High-Speed Video of Cat Tongues Yields Another Reason Why They're Superior
One of the more convenient parts of cat ownership is never (or at least rarely) having to drag your cat into the sink to scrub it clean against its will. This, a recent analysis by scientists at Georgia Tech indicates, is because they posses a unique tools to keep themselves clean. With a tongue like this, they don’t need human help to stay fresh.
In a paper recently published in Proceedings of the National Academy of Sciences David Hu, Ph.D., an assistant professor at Georgia Tech who specializes in biolocomotion takes us deep into the cat grooming process. Using videos captured by high speed cameras (in the above video, 500 frames per second), he showed that cats have a four-phased grooming regimen aided by tiny keratin spikes on their tongues called filiform papillae. Evolution, it appears, really shorted dogs on the tongue front, dooming them to rely upon us to scrub their filth off with our substandard tools.
We’ve known that these papillae exist for a number of years. But this analysis shows that these structures are actually u-shaped, hollow and tilted ever so slightly back towards the throat. This construction allows them to fill up with saliva — if you added all that saliva together, it’s volume is about 1/10th of a eyedropper drop by this paper’s estimate. When a cat licks itself, that saliva is deposited on their body.
The four step process most cats use to groom themselves uses these structures to great advantage. The tongue first extends outwards from the mouth, then expands laterally to which causes the papillae to stiffen until they’re perpendicular to the tongue. Finally, the cat completes a sweeping lick across the fur, depositing the water stored in the hollow cavities in the papillae before retracting the tongue back, where the cavities are refilled with saliva.
The researchers, who actually 3D printed a brush based on the structure of these papillae, were obviously impressed by the elegance of nature’s design on display here. But it also impressed other researchers not involved with the work, like Sunghwan “Sunny” Jung, a bioengineer at Cornell University. He told National Geographic that these papillae address one of the trickier questions in bioengineering: transporting liquids:
“Transporting liquids is a problem for animals and engineers,” he said. “This paper shows that scientists can use the physics of basic animal behavior to answer fundamental questions.”
Generally, animal tongues transport liquid from place to place by capitalizing on water’s surface tension. One study also published in Proceedings of the National Academy of Sciences in 2015 (also using a high speed camera) showed that dog tongues do this by rapidly lapping up water, creating a column that they can then scoop up into their mouths. This study showed that cats actually use a similar process to drink water, though these feature show that their tongues have the added bonus of being able to transport liquid (in this case saliva) in another way.
By comparison, a dog’s single-use tongue is flat, incapable of this, you might say inferior. Though the paper does concede that dog’s tongues are still good at lapping up water from a bowl, which is more than can be said for human tongues.