High-speed videos reveal the strange technique and delicate balance of physical forces cats use to lap milk from a bowl.
Unlike dogs, who use their tongues as ladles to scoop water into their jaws, cats pull columns of liquid up to their mouths using only the very tips of their tongues.
'Cats are just smarter than dogs from the point of view of fluid mechanics,' said civil engineer Roman Stocker of MIT.
Cats' tongues operate more like octopus tentacles or elephant trunks, Stocker found. The study's results could have implications for designing soft, flexible robots.
Stocker grew curious about how cats lap about three years ago while watching his housecat, Cutta Cutta, eating breakfast.
'I started to think, there had to be something interesting about the mechanisms of how the cat was getting the water or milk into the mouth, because it had to overcome gravity,' he said.
Cutta Cutta's tongue flicked in and out of his mouth too quickly for Stocker to study with his naked eye. So he borrowed a high-speed video camera from a colleague at MIT.
Stocker and his colleagues filmed Cutta Cutta drinking a bowl of water mixed with a little bit of yogurt ('for visual contrast and palatability') at 120 frames per second. The results appeared Nov. 11 in Science.
Video: Pedro M. Reis, Sunghwan Jung, Jeffrey M. Aristoff and Roman Stocker
Unlike dogs, who use their tongues as ladles to scoop water into their jaws, cats pull columns of liquid up to their mouths using only the very tips of their tongues.
'Cats are just smarter than dogs from the point of view of fluid mechanics,' said civil engineer Roman Stocker of MIT.
Cats' tongues operate more like octopus tentacles or elephant trunks, Stocker found. The study's results could have implications for designing soft, flexible robots.
Stocker grew curious about how cats lap about three years ago while watching his housecat, Cutta Cutta, eating breakfast.
'I started to think, there had to be something interesting about the mechanisms of how the cat was getting the water or milk into the mouth, because it had to overcome gravity,' he said.
Cutta Cutta's tongue flicked in and out of his mouth too quickly for Stocker to study with his naked eye. So he borrowed a high-speed video camera from a colleague at MIT.
Stocker and his colleagues filmed Cutta Cutta drinking a bowl of water mixed with a little bit of yogurt ('for visual contrast and palatability') at 120 frames per second. The results appeared Nov. 11 in Science.
The videos showed that Cutta Cutta's tongue curled backward like a J as it approached the bowl.
Many scientists assumed the nubs that roughen cats' tongues help in drinking, perhaps by sticking to the water. But the videos showed only the smooth, upper tip of the tongue touched the liquid.
The cat's tongue moved as quickly as 2.5 feet per second, "which is quite incredible," Stocker said.
He lapped between 3 and 4 times a second, and drank about 0.14 milliliters of water per lap.
As Cutta Cutta's tongue returned to his mouth, a column of water was pulled along with it. The column was created by a balance between two forces: gravity, which pulls the liquid back toward the Earth, and inertia, the tendency of a moving object to keep moving unless something stops it.
Initially, inertia is more powerful than gravity, and the column rises with the cat's tongue. But eventually gravity starts to take over, and the column begins to fall back down toward the bowl.
The cat closes his mouth and pinches off the top of the column at just the right second to get the most liquid possible.
"There's a time when the volume of the column is largest, when inertia and gravity just balance," Stocker said. "That's when the cat laps."
Video: Pedro M. Reis, Sunghwan Jung, Jeffrey M. Aristoff and Roman Stocker
See Also:
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- Top 10 Amazing Animal Videos
- Top 10 Incredible Animal Videos: Readers’ Choice
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