No matter which side of the dogs versus cats debate you’re on, one thing is for certain: It’s way more fun to watch a dog drink water. Because canines have floppy jowls instead of complete cheeks, they can’t generate suction with their mouths, so instead they’ve evolved the sloshy, lapping strategy everyone is familiar with. Now, using an array of high-speed cameras and mathematical models, physicists have teased out the fluid dynamics behind how dogs drink. As seen in the video above, a dog curls its tongue posteriorly and plunges it through the water’s surface. When the tongue returns, it drags a column of water up into the dog’s mouth, the team reports today at the American Physical Society's Division of Fluid Dynamics’ annual meeting in San Francisco. The process isn’t as precise as it sounds, as evidenced by the slippery floors of dog owners the world over. Cats actually use a similar lapping strategy, but their tongues never break the water’s surface, which makes for much tidier drinking. That’s not to say cats don’t spill water—they just do it on purpose.
(Video credit: Sean Gart/Virginia Tech, Jake Socha/Virginia Tech, Pavlos Vlachos/Purdue University, Sunghwan Jung/Virginia Tech, and the APS Division of Fluid Dynamics)