When I was a child, my mother saw many snakes grinding a big stone. How did this happen? I want to know.

This is a normal physiological phenomenon. Snakes usually molt once every two or three months. Every time a snake sheds its skin, it will grow up.

Due to the continuous division of mucus layer cells, the snake body forms a new living cell layer and stratum corneum. Under the action of enzymes, the old living cell layer is dissolved, so that the old stratum corneum is separated from the new cell layer. In this way, the snake can grind off the epidermis of the upper and lower jaws with the help of stones or branches in the environment, and gradually turn it back. This kind of snake slough is called dragon clothes in Chinese medicine. There are no sweat glands on the snake's body surface, and it is easy to keratinize. It needs to be skinned 3-8 times a year.

It is found that snakes shed more skin in summer. Because snakes hibernate, they seldom move and grow slowly during hibernation. After the warm weather, they come out to look for food. When hibernating, its nutrients are almost exhausted. In spring, when they come out for activities, the time for body growth begins, so the molting of snakes is concentrated during this time. So there is the phenomenon you mentioned.