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That darn cat!
November 12, 2010 8:36 AM   Subscribe

Scientists have finally discovered tyhe physics of how cats drink.
posted by Daddy-O (51 comments total) 14 users marked this as a favorite

 
"It's a much more delicate and well-controlled mechanism than regular lapping," says Stocker.

Well, of course. You know cats. They wouldn't have it any other way. Too good to lap like all the rest. It helps them maintain their hauty demeanor, don'tcha know.
posted by ifjuly at 8:47 AM on November 12, 2010 [4 favorites]


The cat laps four times a second — too fast for the human eye to see but a blur

That's not really true, is it? I mean, most human eyes can discern movement at that rate just fine, especially something modestly sized like a cat's tongue.
posted by kingbenny at 8:50 AM on November 12, 2010 [1 favorite]


Now that they have this robotic cat tongue, I assume that other cat-tongue-realted research will follow.

Imagine the breakthroughs. Will twenty years find our morning ritals changed to include licking the tongue brush rather than showering? Big tongue-wipers at the waterless car wash? Imagine the time and energy savings! This could be the start of a revolution in cleaning products.
posted by bonehead at 8:51 AM on November 12, 2010 [2 favorites]


Yeah, but how do they eat cheezburgers?
posted by punkfloyd at 8:51 AM on November 12, 2010 [4 favorites]


Yeah, but how do they eat cheezburgers?

No can seez. Iz invisiblez.
posted by XQUZYPHYR at 8:53 AM on November 12, 2010 [16 favorites]


Another good question for scientists is how does my dog survive when her "drinking" technique leaves one hundred percent of the water on the kitchen floor?
posted by Wolfdog at 8:53 AM on November 12, 2010 [23 favorites]


But Roman Stocker, a biophysicist at the Massachusetts Institute of Technology in Cambridge, began to doubt this assumption one morning over breakfast...To better understand the mechanics, Stocker and his team built a rudimentary robotic tongue from a glass disk about the size of the tip of a cat's tongue.

Articles like this make being a scientist sound like fun. "Hey gang, have you ever looked at your cat when it's drinking? I mean, really looked at it?"
posted by The Card Cheat at 8:54 AM on November 12, 2010 [4 favorites]


That's not really true, is it? I mean, most human eyes can discern movement at that rate just fine, especially something modestly sized like a cat's tongue.

The number of times something happens per second isn't the only factor. Consider a blinking light that is on for .24999 seconds then off for .00001 seconds, then repeats. That's technically blinking at 4 Hz, but you'd be hard pressed to discern the blink.

That's an exaggeration for the sake of example, but the point is that the interesting part--the actual movement--may be very fast even though the whole process occurs at a modest 4 Hz.
posted by jedicus at 8:59 AM on November 12, 2010 [1 favorite]


Ok, smarty-scientist, how does my cat manage to drink the water coming out of the tap in the bathroom sink?
posted by orme at 9:01 AM on November 12, 2010 [10 favorites]


The number of times something happens per second isn't the only factor. Consider a blinking light that is on for .24999 seconds then off for .00001 seconds, then repeats. That's technically blinking at 4 Hz, but you'd be hard pressed to discern the blink.

That's an easy fix. All you'd need is a cat equipped with pulse width modulation. Here you go.
posted by Sys Rq at 9:05 AM on November 12, 2010 [5 favorites]


I want to know how my younger cat consistently manages to get water up her nose ever time she drinks.
posted by restless_nomad at 9:08 AM on November 12, 2010 [1 favorite]


The number of times something happens per second isn't the only factor. Consider a blinking light that is on for .24999 seconds then off for .00001 seconds, then repeats. That's technically blinking at 4 Hz, but you'd be hard pressed to discern the blink.

Good point, I'm ashamed to have forgotten that from my engineering background :)
posted by kingbenny at 9:09 AM on November 12, 2010


Although the reporter DID seem to imply it was the frequency that caused it to be a blur to the human eye.
posted by kingbenny at 9:11 AM on November 12, 2010


*Two strangers walk up to cat, demand to know what is the frequency*
posted by lukemeister at 9:14 AM on November 12, 2010 [11 favorites]


Although the reporter DID seem to imply it was the frequency that caused it to be a blur to the human eye.

Oh that's just the usual bad science reporting.
posted by jedicus at 9:20 AM on November 12, 2010


WHAT'S THE FREQUENCY, KITTY?
posted by Faint of Butt at 9:26 AM on November 12, 2010 [12 favorites]


Articles like this make being a scientist sound like fun. "Hey gang, have you ever looked at your cat when it's drinking? I mean, really looked at it?"

That's exactly what is fun about being a scientist! Along with getting a cool result.

However, the remaining 99% is drudgery and dealing with failure.
posted by Turtles all the way down at 9:31 AM on November 12, 2010 [3 favorites]


Ok, smarty-scientist, how does my cat manage to drink the water coming out of the tap in the bathroom sink?

You mean like this?
posted by cazoo at 9:38 AM on November 12, 2010 [10 favorites]


Great. It's good that scientists have been able to explore "how" cats drink.

Now, what I want to know, is "why"?

I mean, is it low self-esteem, genetics, abused as a kitten, what?
posted by mmrtnt at 9:39 AM on November 12, 2010 [16 favorites]


Ok, smarty-scientist, how does my cat manage to drink the water coming out of the tap in the bathroom sink?

I'd be more concened with finding out how the cat turns on the damn faucet.
posted by mmrtnt at 9:44 AM on November 12, 2010 [1 favorite]


The water sticks to the cat's tongue and is pulled upward as the cat draws its tongue into its mouth. When the cat closes its mouth, it breaks the liquid column but still keeps its chin and whiskers dry.

I can attest that this is not true of all cats. My beloved little dope Turtle, who is a total sweetheart but who is Bad At Most Things, drinks as noisily and messily as a Labrador and always ends up with water dripping off her chin after walking away from the water bowl.
posted by mudpuppie at 9:45 AM on November 12, 2010 [1 favorite]


This still doesn't explain why my cat, instead of drinking water straight from the bowl, has to dip his (incredibly hairy) paw into the bowl and then lick it dry, repeating the process until he's slobbered water all over the floor.
posted by daniel_charms at 9:52 AM on November 12, 2010 [3 favorites]


You mean like this?
posted by cazoo at 12:38 PM


Get out of my house!
posted by orme at 9:57 AM on November 12, 2010


This research is not nearly comprehensive enough. My grandparents' old cat Bubba used to drink by sitting next to his water dish, dipping a paw in the water, then slurping from the paw. It was bizarre to see.
posted by brundlefly at 9:57 AM on November 12, 2010 [1 favorite]


It amazes me even more that this lapping mechanism works, given that they don't have a great sense of depth perception in the first place. Mine have to stand next to the water cup (yes, they have a CUP, they like it better than a bowl) and whack it so that the water shakes a little bit, or they're just not sure that there's water in there in the first place.
posted by dlugoczaj at 10:00 AM on November 12, 2010 [2 favorites]


What you probably have there, mudpuppie, is a small Labrador wearing an extremely cunning disguise.

It happens.
posted by Wolfdog at 10:05 AM on November 12, 2010 [4 favorites]


Great. It's good that scientists have been able to explore "how" cats drink.

Now, what I want to know, is "why"?


If you were taken to a strange place, castrated, not allowed to leave, and fed nothing but catfood, you'd drink too.
posted by ChurchHatesTucker at 10:08 AM on November 12, 2010 [15 favorites]


Ok, smarty-scientist, how does my cat manage to drink the water coming out of the tap in the bathroom sink?

Not like this, I hope. That would be silly.
posted by baf at 10:21 AM on November 12, 2010 [3 favorites]


The explanation in the article and video doesn't seem quite right to me. They talk about this being a battle of inertia against gravity, but there is someting else in play here. Otherwise gravity will always win. If the cat's tongue doesn't break (or barely breaks) the plane of the water, isn't it surface tension that causes the water to move up in the little column? The forces are then the lifting force of the cat, the molecular attraction, and gravity against all. In fairness, they allude to this in the beginning of the article, but don't follow up on it.

I mean it's great to make science interesting and popular, but shouldn't a little science be part of it?
posted by Steakfrites at 10:34 AM on November 12, 2010


i was disappointed that video in the link didn't just show me a kitty drinking.
posted by rainperimeter at 10:41 AM on November 12, 2010 [2 favorites]


This still doesn't explain how my cat got into my locked liquor cabinet and lapped up half a bottle of Maker's mark.
posted by Splunge at 10:58 AM on November 12, 2010 [1 favorite]


This still doesn't explain how my cat got into my locked liquor cabinet and lapped up half a bottle of Maker's mark.

Your kid's lying to you
posted by mmrtnt at 11:02 AM on November 12, 2010 [5 favorites]


Surface tension causes the water to stick together in drops - each water molecule can form weak hydrogen bonds with up to 4 others. Fluid inertia causes it to stay put on the rough surface of the cat's tongue, much as a ball of lint would stick to a wool coat. The cat's pulling of the tongue back into the mouth lifts the drop of liquid up, before gravity can overcome the fluid inertia of the droplet - it does not have any 'tendency to keep moving upward,' as the writer suggests. Inertia is the tendency of things to stay put until sufficient force is applied, and fluid inertia just addresses the way liquid changes shape and flows around things compared to solid objects.

If we could persuade the cat to leave its tongue sticking out horizontally and put a droplet of water on it, the droplet would just sit there. It wouldn't migrate along the tongue towards the cat's mouth via capillary action. Cat tongues are covered with thousands of tiny barbs, and these give the water plenty of texture to cling to, such that we could tilt the cat maybe 30 degrees in any direction before gravity would take over. If the tongue were smooth or slimy then the water would roll right off it, just as rain sheets on a newly washed window (smoothed by soap residue) but beads on a dirty one.

This writer either doesn't understand physics or doesn't understand grammar. Either way, this kind of sloppy reporting shouldn't be on the website of the American Association for Advancement of Science. TV and newspapers are bad enough - why is the AAAS publishing and paying for such poor work? Is it any wonder the general public is so ignorant of science, or that we have a shortage of skilled scientists and engineers coming out of our own school system? This is C-grade work, and should be rewritten.
posted by anigbrowl at 11:36 AM on November 12, 2010 [4 favorites]


Cats are weird.
posted by alligatorman at 11:47 AM on November 12, 2010 [4 favorites]


My love for this thread is unexpected and profound.
posted by Halloween Jack at 11:52 AM on November 12, 2010 [2 favorites]


mudpuppie said: Mine have to stand next to the water cup (yes, they have a CUP, they like it better than a bowl) and whack it so that the water shakes a little bit, or they're just not sure that there's water in there in the first place.


One of my cats does this too, albeit with a dish. Sometimes she's too lazy to bat at it herself and if I happen to be in the kitchen she'll stand by the dish and fuss a little to get my attention. I'll tap the dish with my foot and get the water moving for her. I just assumed she liked moving water, rather than the possibility of her not being able to see it. Either way, she certainly has me well-trained.
posted by amyms at 11:54 AM on November 12, 2010


Surface wetting and retention of fluids on biological materials is pretty complex. The spreading physics of fluids is a balance between interfacial tension, fluid viscosit(ies), fluid elasticity and gravity. The point the article makes is that the cat's tongue flick timing is fast enough to lift a lot of water before the fluid has a chance to roll off, rather like scooping-up honey by jabbing it with a stick. Seeing this in action, and better, building a model of this is darn cool, in my estimation.

The interface on a tongue is normally pre-wetted. Would water bead on a cat's tongue? On a tongue surface already wet from previous laps at the water? I don't think so. Water will bead on dry skin, true, however if the surface energy the skin is already lowered by a film of water, a drop won't bead but will spread.

There's a lot of interesting fluid mechanics going on here. There is competition between the interfacial tension of the water with itself (the droplet breaking force), the water with the wetted tongue, the water viscosity, the water elasticity and gravity. The article does a reasonable gloss. I don't have enormous issues with the way it's presented.
posted by bonehead at 12:18 PM on November 12, 2010 [2 favorites]


If you were taken to a strange place, castrated, not allowed to leave, and fed nothing but catfood, you'd drink too.

Someone's been talking to the author of the cat diary.
posted by bearwife at 12:57 PM on November 12, 2010


Hey, @The Card Cheat, I think you've stumbled upon a profound truth about how science works. The greatest revelations in science begin with simple observations coupled with curiosity.
posted by Cataline at 2:18 PM on November 12, 2010


I put my cat into a sealed box with a bowl of water. So now it is either drinking or not drinking in a set of waveforms that are either, thirsty/not thirsty and bowl full/empty.

Or cat is now a bowl, or water cat, or watercatbowl.

Now I'm scared. And I haven't even connected the pellet of poison and the particle-decay trigger.

And the sounds from the box are like the sounds of the universe screaming for my soul.

Perhaps I shouldn't have used a hairless. They are so strange...

Wait. The box is warping. That color isn't a color from this world.

I am going to try to connect the poison pellet device. And I will trigger it by hand. This thing should not...

K̷̫̾ͣ̀i̫̪̼ͣͩ́ͨ̓̆̾t̢͕̝̃t̖̦̪̜̥͊͊́ͅy̜͖̗͑͒ͬ ̷ͣͤ͐ͣw̫̱͔̥̮̻̔͆ͧ̈̎͒͝à̤̥̪͈̲͍͌n̖͓͉͔ͣ͞t̏̌̉҉̦̞̘͍̫͎͍s͚̥̜̗̩̣̯̈́̈ͥ͘ ͍̮̥̃͡t̥͇̲̮̬͋̌̈͒̎̄ǫ͇̲͉̫̳͊͋ͣͥ͛̊ͤͅ ̉ͯ̓̊̕P̳̗̩͛̉͗̾ͪ͞L̮̬̼̍͂̌̇ͦĀ̶̱͕͎̬Y̘̭̮͙̟!̛̯̹̖̱͙̯̜̍̓!͕̖̹͎̩̳͔ͭ̔͌̆͐͝!ͬ!̩͈̲ͮ
posted by Splunge at 2:30 PM on November 12, 2010 [1 favorite]


Steakfrites: I mean it's great to make science interesting and popular, but shouldn't a little science be part of it?

This is AMERICA, bucky - keep your highfalutin "science" out of it!!
posted by Greg_Ace at 4:41 PM on November 12, 2010


we could tilt the cat maybe 30 degrees in any direction before gravity would take over horrible face-ripping pointy claw-filled death ensued

Fixed that for you.
posted by Mr. Bad Example at 4:43 PM on November 12, 2010 [4 favorites]


You can see just how cats drink, as well as Pedro Reis and Roman Stocker explaning their study here [SLDiscovery].
posted by MelanieL at 4:44 PM on November 12, 2010


Also:

Now, what I want to know, is "why"?


What I was always told is that housecats are descended from wild desert cats and as such, have a hunting-for-water instinct that they fulfill by batting the water dish around or drinking from faucets. One of our cats will wait until the very second we turn the shower off and jump in to drink the droplets that trickle out of the faucet. We get very pointed looks from him if we're even a second slow getting out of the tub to dry off.
posted by Mr. Bad Example at 4:46 PM on November 12, 2010


Odd that no mention is made of the role of vacuum and atmospheric pressure in this mechanism.

It seems to me that the actual force that lifts the water droplet against the force of gravity is supplied mainly by atmospheric pressure.

This is clearest from looking at the glass disk model of the phenomenon.

Imagine the glass disk stationary, but just wetted by the surface of the water. Then suddenly you jerk it upwards. Unless water follows the disk upwards, or air rushes in from the perimeter of the disk, a vacuum would form where the disk used to be.

How abhorrent!

The wetting of the disk combined with the surface tension of the water effectively prevents air rushing in from the perimeter during the time the disk is still close to its original position, so pressure at the disk/water interface suddenly drops, and the suddenly unbalanced force exerted by the atmosphere in the body of the water flings a big droplet upward following the disk.

From this perspective, the cat would need that blurring speed as it pulls its tongue back into its mouth. It can stick it out at its leisure.

You'd get some water flung upwards even if the disk was extremely close to the water but not wetted by it, because the aperture for air to rush in from the perimeter would be too small at the very beginning to prevent a partial vacuum from forming-- but the size of the upflung droplet would be much less.
posted by jamjam at 5:47 PM on November 12, 2010


If we could persuade the cat to leave its tongue sticking out horizontally and put a droplet of water on it, the droplet would just sit there. It wouldn't migrate along the tongue towards the cat's mouth via capillary action. Cat tongues are covered with thousands of tiny barbs, and these give the water plenty of texture to cling to, such that we could tilt the cat maybe 30 degrees in any direction before gravity would take over. If the tongue were smooth or slimy then the water would roll right off it, just as rain sheets on a newly washed window (smoothed by soap residue) but beads on a dirty one.

Anigbrowl, the paper (link here) makes it quite clear that the surface used is not the rough part, but the smooth tip of the cat's tongue. So maybe a little less self-righteousness next time?
posted by switchsonic at 6:32 PM on November 12, 2010


it's like the study was ready-made for an IgNoble :)
posted by liza at 7:51 PM on November 12, 2010


Why do scientists need to explore "how" cats drink?
*sigh*
posted by chrisp18938 at 8:51 PM on November 12, 2010


Why do scientists need to explore "how" cats drink?

Science is about discovering the world's subtext. To me, and to most of the scientists I know, the process of inquiry is about discovering the deeper, layered interpretations, models of the world. These models have their own beauty, adding a power and a depth of meaning to everyday things. Sure we have to figure out applications and results to continue to obtain funding, and the work has to be useful, but at a certain level, one of the drivers of science is aesthetics.

When I took the dabblers' painting classes at my local art school, the most important thing the instructor taught me was not how to "draw" (scare quotes fully earned) or colour theory (that was cool), but how to see things differently, how to look at objects not as the thought-cartoon short-cuts we all use in our everyday lives to blot out the huge detail of the world, but as something approaching the things themselves. Shapes, negative spaces, colours.

Science also does that for me. The mechanical process of science is almost always repetitious work that seems closer in spirit to accounting than art. Part of what drives me though are those moments of analysis as precious as those art lessons I fumbled my way though, fresh perspective, understanding.

To me understanding how cats drink is amazing in the same way that understanding how a rainbow works is amazing. Science gives me more ways to "see" the beauty of the world.
posted by bonehead at 9:44 PM on November 12, 2010 [3 favorites]


Well now I am so enlightened, so glad researchers are working hard to push the boundaries of science.
posted by hodenjan at 11:28 PM on November 12, 2010


My cat drinks by scooping the water up with his paw.
posted by Jess the Mess at 6:38 AM on November 13, 2010


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