Cat's delicate lapping defies gravity: study

WASHINGTON (Reuters) - A cat's delicate lapping does not scoop up water but uses inertia to create kind of a backward waterfall, U.S. researchers reported on Thursday.

Their study is more than a curiosity. It could provide insights into ways to robotically move liquids, the team from the Massachusetts Institute of Technology, Virginia Tech and Princeton University said.

When a dog drinks, it forms a cup with its tongue and sloshes water into its mouth -- and, often the floor, as any dog owner can attest.

Cats curve their tongues the other way, so the top of the tongue touches the liquid's surface. Writing in the journal Science, the researchers said they used high-speed videos to analyze how this movement gets water into the cat's mouth.

"Almost everyone has observed a domestic cat lap milk or water. Yet casual observation hardly captures the elegance and complexity of this act, as the tongue's motion is too fast to be resolved by the naked eye," MIT's Roman Stocker and colleagues wrote.

Water will stick to the smooth tip of a cat's tongue. As the cat pulls its tongue up, inertia allows the water to be drawn up in a column, they said.

Controlling the lapping speed helps the cat get the water neatly into its mouth before gravity pulls it back out, they said. A domestic cat manages about four laps a second, while studies of larger cats in a zoo show they lap more slowly.

Understanding such movements help physicists sort out the relationship between gravity and inertia, they said, and can help design robots and other mechanisms.

Was the study a waste of taxpayer dollars?

"We did it without any funding, without any graduate students, without much of the usual apparatus that science is done with nowadays," Stocker said in a statement.

(Reporting by Maggie Fox)