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How Dogs Drink
They’re not so different than cats after all

I love research that reveals surprising similarities between species, especially species often depicted as rivals. Last year, when MIT researchers “discovered” cats had a sophisticated and speedy mechanism for drawing fluid into their mouths, which was one reason they aren’t as sloppy as canines, it just seemed like one more example of the old cats are sleeker, neater, smarter argument.

The thinking was that dogs scooped fluids into their mouths with a backward-curled tongue action. But thanks to weirdly-watchable x-ray videos of dogs drinking, Alfred Crompton and Catherine Musinsky have revealed the dogs do lap like cats. (“How dogs lap: ingestion and intraoral transport in Canis familiaris published in The Journal of Royal Society Biology Lettersabstract free; fee for full report.)

Both dogs and cats use a method called adhesion. “Liquid is transported through the oral cavity to the oesophagus, against gravity, on the surface of the tongue as it is drawn upwards, then a tight contact between the tongue surface and palatal rugae [ridges on the roof of the mouth] traps liquid and prevents its falling out as the tongue is protruded.”

According to a story on Wired’s blog, the commonality goes back to a shared ancestor 43 million years ago. Since that time neither cats nor dogs evolved the thick cheeks now present in many other animals, including humans. “Such cheeks form a tight seal that both retains liquid and allows suction-powered drinking. Without them, cats and dogs needed to develop a different way to drink.”

While the research could impact robot design, it probably won't improve cat-dog relations.


Lisa Wogan lives in Seattle and is the author of, most recently, Dog Park Wisdom.

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Photo and x-ray video of lapping in a dog from AW Crompton on Vimeo.

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