Take a look at this.
It's a dog drinking water. It's also the answer to a riddle. When you and I take a drink, we can lift a glass, hold it to our mouth, tilt and use gravity to pour the water in. Dogs can't do that. In a pinch, we can kneel down, put our mouth to the surface and suck water up (or, to be polite, use a straw). Dogs can't do that either. They don't have sucking ability.
Yet dogs do drink. Oddly enough, scientists weren't sure how they do it.
Once super high speed cameras became available, we could look more closely, and aiming at this dog, we can see it appears to bend its tongue backwards, like an inverted ladle. It dips down, scoops up some water, using its tongue as a pulley. This was a revelation. Because they are dogs, they drool, miss, splash the water — there's nothing polite about a dog drinking — but we seem to have our answer. They scoop! Dogs turn their tongues into ladles. Beautiful!
But wrong. When scientists looked more closely — when they measured — they found that the "scoop" is a delusion. Yes, as Eyder Peralta here at NPR reported a couple of years ago, and as you can see in this short video, the tongue does bend back, but notice a lot (most?) of the water never reaches the mouth. It just slips back to the bowl.
The tongue, it turns out, is not a ladle, but a sticky whip. A dog will extend — no, that's too polite a word — the dog will thrust its tongue into the water and then whip it back up, very, very fast. A stream of water attaches to and follows the tongue upward (adhesion and cohesion) — but only for a fraction of a second. Then gravity kicks in. The rising stream of water loses its upward momentum, and just as it's about to fall back into the bowl, at exactly the point where gravity is about to win, the dog snaps its mouth shut and swallows. Done. The motions are precise, even mathematical.
Engineers have worked out the equation, and when the math says, "Close Your Mouth!" that's when dogs do it. It's as if dogs understand fluid mechanics, and, in their messy doggie way, I guess they do.
Enough About Dogs. What About Cats?
Which brings us to cats.
Cats, it turns out, do the same thing, but being cats, they do it more carefully, more elegantly, more efficiently. No sloshing for them, no puddles outside the bowl. When MIT professor Roman Stocker (working with Pedro Reis) filmed Cutta Cutta, his own cat, drinking, they saw its tongue dip very gently at the milk — no doggie style tongue thrusting, no gouging — just a delicate lap ...
Cats do this very fast — four laps per second — too fast for us to see without a high speed camera. But now that we can measure what's going on, it appears that cats can take in more liquid with less spillage than dogs in the same unit of time. This suggests cats are more efficient (and therefore more intelligent?) lappers than dogs. (Of course, I am aware that the cat in the MIT study was owned — and maybe even loved — by the scientist doing the study. One could imagine, even in the oh-so-rational Civil & Environmental Engineering Department at MIT, Professor Stocker might have just the teeniest cat-admiring bias. I'm waiting for cat-drinking studies done by dog-owning scientists before I'm completely convinced.)
And Now ... The Champions!
But before we get too excited by cats behaving elegantly, I want to move on to pigeons. Cats, I know, eat pigeons. But I recently met three pigeons, who for my money, would embarrass any cat (and every dog) with their extraordinary drinking skills. These three may be the smartest beverage consumers in the small-animal kingdom.
They live (or lived — this picture was taken four years ago) in Brisbane, Australia, and apparently frequented a shopping mall where there is a water fountain. According to the always fascinating blogger Antranik ("Anto" for short), these pigeons watched humans pushing a lever to release water and figured out how water fountains work. They then took turns.
In this shot you see one pigeon sitting on the lever, weighing it down to release some water. The middle one takes a semi-bath dodging in and out of the water, and the third one, on the left, is taking a drink. Then they switched.
Say what you will about sloppy dogs or elegant cats, these three are the Plato, Aristotle and Socrates of the drinking world. Send them to a diner. I bet they'd soon be sucking on straws.