Catty Fluid Mechanics

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Catty fluid mechanics described in articles in BBC News, ScienceNOW and Science DOI: 10.1126/science.119542111 Nov 2010. Using high speed cameras and a robotic device, a group of engineers and physicists from Massachusetts Institute of Technology (MIT), Virginia Polytechnic Institute and Princeton University have worked out how cats lap up liquids. Unlike dogs, which scoop up liquids using their tongues like a ladle, cats rapidly flick their tongues in and out without appearing to scoop up the liquid. High speed photography revealed that cats curl their tongue downwards so that the upper surface just touches the water without penetrating the surface. When the cat lifts its tongue it pulls up a column of water and then captures this by closing its mouth.

The researchers then built a mechanical device the size of a cat’s tongue to study the physics of the water movement. They found it involves a balance between the forces of inertia and gravity. Roman Stocker, a biophysicist from MIT explained: “The creation of the water column is driven by the force inertia - the tendency of the liquid, once in motion, to keep going. The water column initially becomes larger in length and in volume, but at some point the weight of the column itself overcomes these inertial forces, and gravity causes the column to collapse back into the bowl. There is a time when the volume of a column is at a maximum, which is the time at which the cat closes its jaw.”

The team studied larger members of the feline family in the zoo and wild animals recorded on video clips, and discovered the “big cats” also use the same method of drinking. The researchers suggest that cats developed this method of drinking because they don’t like getting their faces splashed with water. Stocker explained: “The lapping mechanism of cats seems to be a lot cleaner compared with dogs, which is much more vigorous and produces more splash. One speculation is the face of the cat, and particularly the region around the nose and the whiskers, is extremely sensitive, therefore the cat might want to try and keep that as dry as possible.” He added: “I would say cats know more about fluid mechanics than dogs.”


Editorial Comment: We would say cats (and dogs) know as much about fluid mechanics as the mechanical device used in the research knows about fluid mechanics – precisely zilch! It was the engineers who intelligently designed the device who understood the fluid mechanics. In the same way it is the Creator of the cat who made the cat’s tongue and wired its brain to make the required movements to use fluid mechanics to drink, who had the understanding long before we figured it out. (Ref. design, physics, mammals)

Evidence News 15 Dec 2010