Cats master the fine art of drinking – but dogs know how to keep dry
A toast to cats and their amazing abilities! Just try drinking without using your hands or a straw. Most likely, you’ll end up with water all over your face, your hair soaked, and coughing and spluttering from water going up your nose.
Dogs do it better, curling their tongue into the shape of a spoon and getting a tongueful of water with every lap.
But cats … ah yes, once again, cats go really hi-tech.
It took four of the nation’s top engineers – Roman Stocker and Pedro Reis of the Massachusetts Institute of Technology, Sunghwan Jung of Virginia Tech, and Jeffrey Aristoff of Princeton University – to figure it out … with help from Stocker’s cat, Cutta Cutta (Aboriginal Australian for “Stars Stars”).
The results, published in Science Daily, were all over the news this week. Here’s what they learned:
The tip of the cat’s tongue barely brushes the surface of the water before the cat rapidly draws her tongue back up, thus forming a column of rising water. At precisely the right moment, she closes her mouth to catch the column of water.
Cutta Cutta takes a drink. The video is slowed down by a factor of 12.
It’s a delicate balance between inertia (the tendency of the water to keep moving in the direction it’s going) and gravity (which causes it to fall back down). A cat knows exactly how fast to move her tongue to create the column. Different sized cats need a different mathematical equation. Your average housecat does about four laps per second; large cats like lions lap more slowly. After videoing all kinds of cats, the researchers developed a mathematical model that characterizes the ratio between gravity and inertia and established that in all cases, the cats were maintaining a perfect balance.
The scientists were effusive in their comments to Science Daily:
“Cats are smarter than many people think,” said Aristoff, “at least when it comes to hydrodynamics.”
“We were surprised by the beauty of the fluid mechanics involved in this system,” said Jung.
“They really know how to do it perfectly,” said Reis, “almost as if they’re doing the equations in their heads.”
And Stocker, who is understandably proud of his kitty, Cutta Cutta, commented on the way the project was managed. “We did it without funding, without any graduate students and without much of the usual apparatus that science is done with nowadays.”
More pet physics!
David Hu, a researcher at Georgia Tech, is a dog person.
“I have no idea why cats don’t just do it the ordinary way,” he said. “I think that dogs generally have a better way to do it.”
Hu, who has a poodle, has been studying how dogs shake themselves dry. And he’s demonstrated that dogs – and indeed furry animals of all kinds – have that particular science down to a fine art, too. They do it so well, in fact, that washing machine designers are taking note. “The equations that govern the fluid motion inside [washing machines] are too complicated to solve,” Hu explained.
Hu’s team used high-speed videography to see how dogs and other furry animals get dry fast. (Nature has been working on this for millions of years. After all, in the wild, getting dry fast on a cold day can be a matter of life and death.)
As anyone who has given their dog a bath has observed, shaking begins at the head and proceeds down the body, ending with flicks of the tail. The scientist’s research showed that starting at the head provides a solid point for the energy wave to propagate down the animal’s body. And the head can also twist more than the rest of the body, resulting in higher amplitude waves. Very furry animals tend to have looser skin, which whips around and creates greater acceleration as the animal shakes one way then the other.
As with the cat drinking experiments, Hu’s team learned that animals with smaller bodies must shake faster. And again the animals have figured out the best frequency to suit their size.
The research will be presented in detail at the upcoming Annual Meeting of the American Physical Society.