Friday, November 19, 2010

fun friday feline factoid - how cats drink

Researchers from MIT, Virginia Tech and Princeton joined forces to determine just how exactly cats consume liquids (see MIT press release for more info, pictures and video). Their results are fascinating and prove that cats are experts at hydromechanics.

The mechanism used to get the liquid is amazing. A domestic cat averages about four laps per second. Each lap yields about 0.1 milliliters of liquid. Research by a MIT researcher back in the 40's indicated that cat's use their tongue to ladle water into their mouth but this recent research debunks that theory.
Recent high-speed videos made by this team clearly revealed that the top surface of the cat’s tongue is the only surface to touch the liquid. Cats, unlike dogs, aren’t dipping their tongues into the liquid like ladles after all. Instead, the cat’s lapping mechanism is far more subtle and elegant. The smooth tip of the tongue barely brushes the surface of the liquid before the cat rapidly draws its tongue back up. As it does so, a column of milk forms between the moving tongue and the liquid’s surface. The cat then closes its mouth, pinching off the top of the column for a nice drink, while keeping its chin dry.

The liquid column, it turns out, is created by a delicate balance between gravity, which pulls the liquid back to the bowl, and inertia, which in physics, refers to the tendency of the liquid or any matter, to continue moving in a direction unless another force interferes. The cat instinctively knows just how quickly to lap in order to balance these two forces, and just when to close its mouth. If it waits another fraction of a second, the force of gravity will overtake inertia, causing the column to break, the liquid to fall back into the bowl, and the cat’s tongue to come up empty. 
The scientists also videotaped larger cats to study their drinking practices. With the collected data they were able to create a mathematical relationship based on the size of the animal.
With these videos slowed way down, the researchers established the speed of the tongue’s movement and the frequency of lapping. Knowing the size and speed of the tongue, the researchers then developed a mathematical model involving the Froude number, a dimensionless number that characterizes the ratio between gravity and inertia. For cats of all sizes, that number is almost exactly one, indicating a perfect balance.
Here is a video of a cat drinking, in very slow motion. This is truly amazing.

Wow, I am amazed.

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