Fluid mechanics help cats get the cream

When it comes to bio-mechanics, cats have got dogs licked.

That’s the conclusion of Roman Stocker, a biophysicist at MIT. He decided to investigate why cats are able to lap up liquids in such a graceful way, while dogs splash it everywhere.

Many animals have to use their tongues to lap up water because, unlike humans, they don’t have cheeks that allow them to close their mouths enough for suction. But thanks to Stocker’s work with a high speed camera, it’s now become clear that cats don’t lap in the same way as most.

Whereas a dog’s lapping tongue motion is not more sophisticated than the way humans eat soup with a spoon (stick it in, scoop it up, place in mouth), it turns out that a cat curls the tip of its tongue backwards rather than forwards. Only the front side of the very tip the tongue ever touches the liquid, and even then doesn’t penetrate it.

Instead, the tongue sticks to the liquid and the cat then pulls the tongue upwards quickly enough that the liquid is drawn up in a column. The cat then closes its mouth and thus captures the section of the column that has passed its lips.

Stocker and colleagues then attempted to recreate the technique with a robotic “tongue.” They discovered it’s a difficult balance, as there’s a battle between the inertia caused by the motion and the gravity affecting the column. Further study of the video of cats, plus the drinking techniques of leopards, tigers and other “big cats”, showed that felines appear to be able to judge this balance perfectly, closing their mouth at the point that gives them the most amount of liquid before the column collapses.

Why cats use such a refined technique isn’t known for certain. One theory is that its to avoid splashing water onto the sensitive area around the nose and whiskers.

[Cat picture via Flickr (CC)]

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