I meant to post this in February, but got super busy with qualifying exams, lab, and life!
Curiosity filmed the cat:
High-speed imaging explains the physics behind cat drinking
Cats are known for their mysterious habits - from their constant grooming of themselves to always landing on their feet. Only recently have scientists actually uncovered the exact physics of one such feat: felines’ ability to lap up liquids, spill-free.
A film made in 1940 by MIT electrical engineering professor Harold Edgerton hinted at the fact that there was something intriguing about cat lapping that involved the contour of the tongue. It took 60 years, the help of high-speed imaging, and a team of 4 engineers from MIT, Virginia Tech and Princeton to finally discover the crucial aspect of the lapping phenomenon as described in the November 11, 2010, issue of Science.
The study stemmed from a casual observation by the head of the research group, Roman Stocker, whose actual research at MIT focuses on the movements of ocean microbes. He was fascinated by how his cat Cutta Cutta (“star star” in an Australian aboriginal language) drank liquids, especially since felines have incomplete cheeks. Vertebrates with incomplete cheeks must use their tongue to pull the liquid into their mouth, unlike us humans who have complete cheeks that allow for suction to draw in the liquid.
Stocker’s initial curiosity turned into an actual scientific study when he was able to convince three other researchers to use high-speed imaging (a technology readily available to them) to capture the fluid dynamics of Cutta Cutta’s lapping. They observed that the cat’s tongue bent slightly back, allowing the top of the tip of the tongue to just slightly adhere to the liquid surface (the only region of the tongue to do so). After contact, the cat immediately lifted its tongue, creating a thin stream of liquid that was pulled upward into the mouth. The researchers claim that the pulling motion is inertia-driven, allowing for more liquid to follow after the tongue leaves the liquid. Gravity tries to counter the upward motion of the column, but inertia overcomes the downward force when the cat quickly closes its mouth, allowing for the most liquid to get trapped in its mouth. This phenomenon was observed with other cats as well.
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| Usually cats lap up water from a bowl, but this feline drinks it straight from the tap! Photo courtesy of Elizabeth Winograd-Cort. |
The intricate physics behind this lapping motion explains why cats exhibit such finesse while drinking, unlike dogs who also have incomplete cheeks but make such a mess quenching their thirst. Dogs curl their tongues in the form of a ladle to scoop up the water into their mouths. This is not the most efficient way of obtaining water – liquid is bound to splash over the sides of the tongue. But we still love our dogs despite this flaw.
Although the researches had performed this study for fun (no funding was required, no graduate students were used as slaves, and the high-speed imaging device already existed, as well as the cats!), they definitely see potential biomedical applications and even insight into the evolution of mammalian feeding from these results.
