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High-speed video reveals how cats lap milk

Posted on behalf of Gozde Zorlu

Cats perform a remarkable feat of physics every time they take a drink, according to research into the unique way that our feline friends lap their milk.

Using high speed imaging, scientists have watched how a cat’s tongue forms into a j-shape and merely brushes along the surface of the liquid – unlike a dog, which uses its tongue as a ladle to scoop up the liquid. Once the liquid sticks to the cat’s tongue, it is pulled upwards at a rapid speed of about one meter per second, creating a column of liquid. The cat then captures a mouthful by pinching off the top of the column.

“I was watching my cat lapping during breakfast when it occurred to me that there were interesting biomechanics behind that simple action, and it snowballed from there,” says Roman Stocker, an engineer at the Massachusetts Institute of Technology (MIT) in Cambridge, and one of the authors of the study, published today in Science.

The cat needs split-second timing to get its mouthful. As gravity overcomes the momentum of the rising column of liquid, the column breaks away from the tongue and begins to fall, potentially depriving kitty of its meal.

After recording a variety of cats drinking liquids, the researchers developed a model to predict the cat’s lapping frequency (see videos). They found that the lapping frequency is determined by the typical size of the liquid column and the ratio of inertia and gravity – and is almost perfectly tuned to maximise the amount of liquid the cat can drink.

The researchers also recorded larger felines in nearby zoos in the Boston area, and scoured YouTube for video clips of large cats including lions, tigers and jaguars lapping, captured by tourists on safari parks in Africa. “Some cats are easier to film in the wild,” explains Pedro Reis, an MIT engineer who also worked on the study. Whatever the size of the cat, the model correctly predicted its lapping frequencies, with bigger cats lapping more slowly than their domestic cousins.

Why would cats use this technique to get a drink? From an evolutionary point of view, “the cat’s lapping action is cleaner than a dog’s splashing, and there is value in keeping the whiskers dry because they are highly sensitive sensory preceptors,” says Reis.

The mechanism doesn’t just provide an insight into how cats drink – it could also provide inspiration for new ways of transporting fluids. “From an engineering perspective, this would be important for moving small quantities of fluid that are very sticky or precious – blood, or hot soup, for example – in which one wants to minimize touching fluid and solid,” says David Hu, a mathematician and mechanical engineer at the Georgia Institute of Technology in Atlanta.

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    Mary said:

    It says the videos are unavailable when I click to watch.

    ?

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