CSB #3: How Do Cats Drink Water?

Definitions: 

1.) high speed photography - a way of taking clear pictures of a very fast action. 

2.) Froude's number - a dimensionless number comparing inertia and gravitational forces. 

3.) hydrodynamic - relating to the force of liquid in motion.

Summary: 

How do cats drink water? Animals like us humans drink liquid by creating suction in our mouths, which is only made possible if the animal can close its mouth fully. However, cats cannot do this and so four scientists, Pedro M. Reis and Roman Stocker of the Massachusetts Institute of Technology, joined by Sunghwan Jung of the Virginia Polytechnic Institute and Jeffrey M. Aristoff of Princeton joined together to find out how exactly cats "lap" water. Last Thursday, the engineers reported that "the cat’s lapping method depends on its instinctive ability to calculate the point at which gravitational force would overcome inertia and cause the water to fall." What happens is that the cat touches the liquid with the smooth tip of its tongue and flicks it upwards, bringing along with it a column of liquid (see picture above). Right before the column begins to fall, the cat snaps its mouth shut, consuming 3/100 of a tablespoon. This is a significant amount, considering that a cat laps 4 times a second. Using a piston and a glass plate at the end of it, the engineers mimicked the cat's lapping to find the speed of tongue movement that would get the most water; it turns out that the speed they found was exactly the speed of an average cat's lapping: 1 meter per second. The engineers also developed an equation that would calculate how fast a cat would have to lap in comparison to its size. Going to the Zoo New England, they used the equation to find the speeds for lions, leopards, jaguars and ocelots, and their predictions were correct. 

Discussion:

I find the fact that the way a cat drinks water, an action that seems so simple but is actually complex, perplexing. Unlike dogs, cats lap their water/liquid much classier than dogs do. Dogs stick their tongues out and form a crude cup/bowl and bring the small amount of water back in to their muzzles. I never thought that a cat would have a natural instinct about gravitational pull and inertia. The fact that the engineers also found a complex equation to find what speed a tongue must go in order for optimized effects is amusing to me, almost satirical. All of this research and study was started from Cutta Cutta, Stocker's cat. While having breakfast, he wondered what hydrodynamic problems the cat might be solving as it drank its water, and so the study began. 

Questions: 

1.) How did the engineers come up with the equation?

2.) Do all cats drink water like this? Are there any exceptions?

Sources:

Article:

Wade, Nicholas. "For Cats, a Big Gulp With a Touch of the Tongue." The New York
     Times. The New York Times, 11 Nov. 2010. Web. 16 Nov. 2010.
     <http://www.nytimes.com/2010/11/12/science/12cats.html?_r=2&ref=science>.   

Image: 

http://www.nytimes.com/2010/11/12/science/12cats.html?_r=2&ref=science