Why do cats and dogs lick water with their tongues?

The face and lips of human beings (including some primates) can form a perfect straw shape, so absorbing water is much more efficient than licking water. But cats and dogs have big mouths, no lips and no complicated facial muscles to help them, so they can't absorb water at all.

Recently, scientists have carefully observed the drinking behavior of cats and dogs with high-speed photography and found that they are not actually licking. They put their tongues into the water first, then the tip of the tongue bends backward and quickly retracts their tongues, which will suck some water into their mouths. This "suction" takes advantage of the surface tension of water. We can simulate this process by hand in the washbasin: put your palm flat on the surface of the water, let the water just pass the back of your hand, and then raise your hand quickly, and you will find that the water is "sucked" away. In this way, cats and dogs can actually drink water quickly.