German shepherd-husky mix puppies make a mess of their water bowl. (Defense Department)
SAN FRANCISCO, Nov. 25 (UPI) -- It's a question that's dogged scientists for decades. Why do dogs make a mess of their water bowl? The answer is not the domain of evolutionary biologists or animal behaviorists, but physicists.
Scientists already knew how cats quench their thirst -- daintily and precisely, of course. A 2010 study conducted by engineers from Princeton and the Massachusetts Institute of Technology showed that felines touch their tongue to the water surface without penetrating it. When they retract their tongue, a thin column of water is pulled up towards their mouth at a speed of 3 feet per second. Just as gravity threatens to pull the water back down, cats quickly close theirs mouths shut and swallow. They can do this four times per second.
While cats extract their water, sassily and with the exactness of sniper, dogs splash and slosh their way through a bowl of water. But what's so different about their technique? Scientists at Virginia Tech and Purdue set up lab experiments to find out.
"When we started this project, we thought that dogs drink similarly to cats," said lead researcher Sunny Jung, an assistant professor at Virginia Tech. "But it turns out that it's different, because dogs smash their tongues on the water surface -- they make lots of splashing -- but a cat never does that."
The work of Jung and his colleagues showed that dogs gain one advantage by breaking the surface of the water with force -- besides the fun of sloshing water out of the bowl and all over the floor. They draw water up at a greater rate. Cats' tongues produce a water column that accelerates upward at a rate of two to four times that of gravity. Dog's tongues pull water upward at a rate of five to eight times that of gravity.
By watching dogs drink up close, Jung and his colleagues always found that dogs allow the water column to just begin to break, as the bottom and top separate. Dogs close their mouths over the top half just as it begins to fall back to the bowl.
Jung and his team of physicists shared their findings Tuesday with attendees at the annual meeting of the American Physical Society's Division of Fluid Dynamics, held in San Francisco.
