Editorial
Front Page - Friday, December 3, 2010
I Swear...
Cat-lapping mystery solved
Vic Fleming
Roman Stocker was hardly a household name before the Nov. 11 issue of Science came out.
According to the Massa-chusetts Institute of Technology Web site, Stocker is an Associate Professor in the Environmental Microfluidics Group of MIT’s Department of Civil and Environmental Engineering. A mouthful, that’s what his title is (but wait till you get to his associates’).
Anyway, it seems that sometime in 2007, Prof. Stocker was watching his family cat, Cutta Cutta, lap water from its bowl when a thought occurred to him: “I wonder what hydrodynamic problems Cutta Cutta is solving.”
He contacted Pedro Reis, the Esther and Harold E. Edgerton Assistant Professor of Mechanical Engineering and Civil and Environmental Engineering at MIT’s Elasticity, Geometry and Statistics Laboratory (told you).
Presumably, Roman said something like, “Hey, Pedro, did you ever watch cats drink and wonder what’s up with that tongue thing they do?”
Game on!
They brought a couple others on board, going out of state to do so.
Sunghwan Jung is an Assistant Professor of Engineering Science and Mechanics at Virginia Polytechnic Institute.
Jeffrey Aristoff is the NSF Mathematical Sciences Postdoctoral Research Fellow in Complex Fluids Group of the Department of Mechanical and Aerospace Engineering at Princeton University.
During a three-and-a-half-year period, these guys researched and wrote a paper, now published as “How Cats Lap: Water uptake by Felis catus.”
Thus, we do in fact now know how cats drink. Aside from the fact that they lap water so fast that humans cannot follow what’s going on.
It took high-speed photography to show that cats, which, like most carnivores, cannot fully close their mouths to create suction, lap four times per second at a speed of about 3 feet per second.
It took more than the photos, though, to show what was happening.
When my dog Maggie is
thirsty, she makes a lot of noise lapping water from her bowl. Thanks to Stocker, et al, and New York Times reporter Nicholas Wade, I now know that she forms a sort of cup with her tongue and hauls the water into her muzzle.
Cats, though, the researchers conclude, are “classier.”
A cat’s “lapping method,” they say, “depends on its instinctive ability to calculate the balance between opposing gravitational and inertial forces.
“What happens is that the cat darts its tongue, curving the upper side downward so that the tip lightly touches the surface of the water.
“The tongue is then pulled upward at high speed, drawing a column of water behind it. Just at the moment that gravity finally overcomes the rush of the water and starts to pull the column down - snap! The cat’s jaws have closed over the jet of water and swallowed it.”
The cat-lap research team tested its findings with a machine that mimicked a cat’s tongue. This required calculation of a “Froude number,” which (per Wikipedia) is “the ratio of a characteristic velocity to a gravitational wave velocity” and which “may equivalently be defined as the ratio of a body’s inertia to gravitational forces. In fluid mechanics, the Froude number is used to determine the resistance of an object moving through water, and permits the comparison of objects of different sizes.”
They predicted “how fast a cat should lap to get the greatest amount of water into its mouth.” Their prediction, it turned out, was spot on.
They then turned to whether their findings would translate to larger cats.
They determined a formula: “The lapping frequency should be the weight of the cat species, raised to the power of minus one-sixth and multiplied by 4.6.”
With formula in hand, they developed connections with some zoos, shot footage of lions and leopard and ocelots, and validated their formula and predictions derived therefrom.
So, all you moms and dads who read this column, if you were thinking of doing this for your kid’s next science fair project, forget it! It’s been done.
Vic Fleming is a district court judge in Little Rock, Arkansas, where he also teaches at the William H. Bowen School of Law. Contact him at vicfleming@att.net.
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