Cats are Water Wizards
Water is essential to survival and land animals have evolved to meet their water needs in various ways. Some absorb water through the skin, some extract water from the moisture in their food but most animals rely on drinking water to stay hydrated.
At first you might say, well of course animals drink water, but when you start to think about it, the simple act of drinking presents a challenge because fresh water is mostly a horizontal liquid surface in puddles, ponds, lakes and streams so animals must work against gravity to get the water up off the ground and into their mouths. This simple act of survival is actually a remarkable achievement.
It is physically impossible for a cat to suck.
Vertebrates (animals with backbones) use their tongue in two distinctly different ways. Vertebrates with complete cheeks, such as pigs, sheep, and horses, use suction to draw liquid upward and use their tongue to transport it into the mouth. However, vertebrates with incomplete cheeks, including most carnivores (cats are carnivores), are unable (after weaning) to seal their mouth cavity to create suction and therefore rely on their tongue to move water into the mouth. It is physically impossible for a cat to suck.
When the tongue sweeps the bottom of a shallow puddle, the process is called licking. When the puddle is deeper and the tongue cannot reach the bottom, it is called lapping. Even if you have watched your cat lap water, you might not have been fully aware of the complexity of the maneuver because the cat tongue’s motion is too fast for the naked eye.
Dr. Roman Stocker, a biophysicist from the Massachusetts Institute of Technology, was inspired to investigate the physics of cat laps after watching Cutta Cutta, a cat sharing his own habitat drinking water. Here is what Dr. Stocker found to be happening when your cat drink’s or rather laps water.*
With their face in a downward position the cat sticks out their tongue with its tip curled sharply. At the lowest position of the tongue’s tip, its dorsal (bottom) side rests on the liquid surface, without piercing it. When the cat lifts the tongue, water adhering to the dorsal side of the tip is drawn upward, forming a column. This water column is further extended by the tongue’s upward motion, thinning in the process, and is finally partially captured upon jaw closure. The water is trapped between the roof of the mouth and the tongue until it is swallowed.
Here is a short video demonstrating the remarkable cat tongue.
The researchers discovered that big cats such as tigers, leopards and cheetahs also use the same elegant method as their domestic cousins to intake water. However, it is no surprise that dogs use their tongues in a less refined way than cats. The dog splashes and carries on in a more vigorous and raucous method of scooping water into their mouths making noise and a mess.
Dr Stocker and his colleagues speculate that cats might have developed this sophisticated method of drinking based on their dislike of water and/or the desire to keep the super sensitive area around the nose and whiskers as dry as possible. But perhaps the cat just has a better understanding of physics and fluid mechanics than the dog.
*Reis, P. M., Sunghwan, J., Aristoff, J. M., & Stocke, R. (2010). How Cats Lap: Water Uptake by Felis catus. Science, 330(6008), 1231-1234. doi:10.1126/science.1195421