Why Do Dogs Make a Mess When They Drink?

Using video, photography and simulations, researchers have pinned down the mechanics behind how dogs drink water.

Anyone who has ever witnessed a dog drinking from its water bowl knows that taking a simple sip of water can be a messy affair full of splashing and chomping.

Well as it turns out, using video, photography and laboratory simulations, researchers at the Virginia Tech College of Engineering have discovered that the sloppy-looking actions at the dog bowl are in fact high-speed, precisely timed movements that optimize a dog’s ability to acquire fluids.

The discovery appeared in the scientific journal Proceedings of the National Academy of Sciences in December and built upon previous studies of the drinking mechanics of cats and dogs.

“We know cats and dogs are quite different in terms of behavior and character,” said Sunghwan “Sunny” Jung, an associate professor of biomedical engineering and mechanics at Virginia Tech. “But before we did fundamental studies of how these animals drink fluids, our guess was dogs and cats drink about the same way. Instead we found out that dogs drink quite differently than cats.”

According to the study, dogs and cats are biting animals and neither have full cheeks. But without cheeks, they can’t create suction to drink — as people, horses, and elephants do. Instead they use their tongues to quickly raise water upward through a process involving inertia.

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Both animals move their tongues too quickly to be completely observe by the naked eye, but dogs accelerate their tongues at a much faster rate than cats, plunging them into the water and curling them downward toward their lower jaws. They quickly retract their tongues and a column of water forms and rises into their mouths. Dogs precisely bite down to capture the water, and in an instant, they reopen their mouths and immerse their tongues back into the water.

Cats, on the other hand, lightly touch the surface of the water with their tongues, usually never fully immersing them, according to previous imaging by Jung and other researchers. When their tongues rise into their mouths, liquid adheres to the upper side, forming an elegant water column.

“Dog drinking is more acceleration driven using unsteady inertia to draw water upward in a column, whereas cats employ steady inertia,” Jung said.

Dogs also curl the underside of their tongues to bring a tiny ladle of water upward. When dogs accelerate their tongues upwards, the latest research reveals a water column rising, but some water remains in the ladle of the tongue and is tossed to either side of the dog’s mouth or falls downwards.

Although dogs do not use their tongues to actively scoop water into their mouths, it is possible that the scooped liquid has some positive effect on the water column dynamics below the tongue, the researchers said.

So the next time you yell at Fluffy for making a mess at the water bowl (or the toilet bowl for those not so well-trained canines) consider it a small side effect of a carefully orchestrated evolutionary adaptation.

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