A video of a male leopard drinking on the 9th of March 2016. Leopards do not drink as often as lions as they would get most of their moisture needs from the prey they eat. They would however drink water when readily available and enjoy having a drink after a good meal like most mammals do. The best time to find predators drinking is at sunset just after they would be waking up after a whole day’s rest. Their prey know this and would avoid waterholes preferring to drink late morning and mid afternoon.
Although cats are not the most efficient drinkers and it usually takes a while for them to quench their thirst, the physics behind the process is mind boggling. Cats can’t create suction to drink the way humans do. They use fluid mechanics instead to efficiently lap up water while dogs use their tongue kind of like a spoon lifting water into their mouths.
It is known that when cats lap, they extend their tongues straight down with the tip of the tongue curled backwards, so that the top of the tongue touches the liquid first. That insight came from a 1940 film of a cat lapping milk, made by Harold “Doc” Edgerton, the MIT electrical engineering professor who first used strobe lights in photography to stop action. That film appeared as part of an MGM-released movie called Quicker’n a Wink, which won an Academy Award in 1941. But recent high-speed videos made by MIT, Virginia Tech and Princeton researchers reveal that the top of the cat’s tongue is the only surface to touch the liquid.
When the cat’s tongue touches the liquid surface, some of the liquid sticks to it through liquid adhesion, much as water adheres to a human palm when it touches the surface of a pool. But the cat draws its tongue back up so rapidly that for a fraction of a second, inertia — the tendency of the moving liquid to continue following the tongue — overcomes gravity, which is pulling the liquid back. The cat instinctively knows just when this delicate balance will change, and it closes its mouth in the instant before gravity overtakes inertia and the liquid would fall back. While the domestic cat averages about four laps per second, the big cats such as leopards know to slow down. Because their tongues are larger, they lap more slowly to achieve the same balance of gravity and inertia.
So next time you see your cat or maybe even a leopard drinking stop to think about the wonderful physics going on when witnessing such an uncomplicated looking process.