Science explains what makes dogs such sloppy drinkers

dog drinking water

GULP  Dogs lapping liquid use their tongues to draw up a column of water and then bite off a drink very close to what scientists calculate as the perfect moment. 

Jake Socha, Sean Gart and S. Jung

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A dog lapping water with all that ga-lunk ga-lunk splashing has some hidden precision in the inevitable mess.

“We cannot train dogs to drink nicely,” says fluids scientist Sunghwan Jung of Virginia Tech in Blacksburg.  Dogs (and cats) can’t close their wide mouths securely enough to suck up liquids, so they lap them up instead. Lappers reach out with the tongue and then retract it quickly, drawing up a thin column of water underneath.

 Just when that column of water is about to collapse back into a water dish, a dog snaps its jaws closed, capturing the water, Jung and his colleagues report December 14 in the Proceedings of the National Academy of Sciences. The researchers recognized the precise timing after filming 19 dogs, from a Yorkshire terrier to a Great Dane.

The films also showed what makes dogs so splashy. The dogs plunge a lot more surface area of tongue into the liquid than cats do. And dogs retract their tongues with acceleration up to four times that from Earth’s gravity.   

SPLASH, SLOP Cameras looking up from the bottom of a dog bowl and from the side show the extensive tongue surface area plunged into the water and other factors that make dog lapping so messy. S. Gart et al/PNAS 2015

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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