High-Speed X-Ray Video Reveals Secret to How Dogs Drink

Dogs aren't the world's most dainty drinkers. Give a thirsty dog a bowl of water and get out the umbrella. The tongue scoops, the water...

Maria Goodavage  |  May 25th 2011

Dogs aren’t the world’s most dainty drinkers. Give a thirsty dog a bowl of water and get out the umbrella. The tongue scoops, the water splishes and sploshes everywhere. Cats, on the other hand, seem to have a quiet elegance to their drinking. It’s almost meditative to some cat owners.

But this is not the time for cats to start feeling a smug superiority. (Well, no more than usual.) Science is revealing that cats and dogs both use the same techniques to get water into their mouths. Cats just tend to do it with more grace.

A study in the journal Science last year explored the science behind the cat lap. Using high-speed video, researchers were able to dramatically slow down footage of a cat drinking. They found that when the tip of a cat’s tongue barely touched the water’s surface, the water stuck to it. When the cat pulled her tongue back in, the movement created a water column on the back of her tongue, and the cat snapped her jaws around it after every lap before it could fall out.

Researcher Alfred Crompton, of Harvard University’s Museum of Comparative Zoology, wanted to see how different the water-guzzling experience was for dogs. Scientists and most dog owners have assumed that a dog uses his tongue as a ladle, scooping up liquid in a haphazard, decidedly doggy way, with none of the finessed fluid mechanics employed by felines.

So Crompton took a high-speed camera and an X-ray camera and let his dog Matilda enjoy a big cylinder of broth. (See video above.) “At first, it looked like dogs were scooping, but that is a snare and a delusion,” he said in a BBC article.

Interestingly, it turns out that the water that was collected in the ladle part of Matilda’s tongue dropped off her tongue before hitting her mouth. It turns out dogs use their tongues to get the conveyor-belt-like flow of liquid down his throat just as a cat does, Crompton reported in the Journal Proceedings of the Royal Society Biology Letters.

The main difference was that while a cat’s tongue barely touches the liquid, a dog’s plunges all the way in, willy-nilly.

He explained in a BBC article that the difference may boil down to lifestyle habits in general: “Cats are just a little more particular about the mess they make. They always like to be neat and clean and to tidy themselves up. They curl their tongue backwards and lay it onto the surface of liquid without penetrating it, so they don’t make a mess.

“Dogs on the other hand are a bit more exuberant – they don’t worry about spreading the liquid around and making a mess.”

But what happens when water is in a dog’s mouth is pretty astounding. I’ll let an article in LiveScience explain:

They found that dogs take a few laps before they actually swallow. Once the liquid is in the mouth, the dog brings its tongue in contact with the roof of its mouth, trapping the liquid between its tongue surface and the ridges on its palate. Then the dog extends its tongue again, still keeping it in contact with the roof of its mouth.

“This is the really cool part,” Musinsky told LivesScience. “Because the tongue is maintaining contact, but it’s also sliding out of the mouth.”

As the dog brings another chunk of liquid up with its tongue, the tongue drops away and the first bit of liquid goes to the back of the mouth. Repeating the cycle again, the dog brings a new sip of water to the front of its mouth, swallowing the first lap of water and moving the second toward its throat.

“You’ve used the tongue and palate as sort of a conveyor belt,” Crompton said.

You can see this mechanism at work in the video above.

So next time your dog goes to whet his whistle, you can watch him and admire him for everything he has to do to get it from bowl to throat.

Just don’t get too close while he’s doing it.