Skin of snakes consists of outer epidermis and inner dermis. The inner dermis (soft, fibrous and pliable) contains pigment cells that give characteristic colour patterns. The outer epidermis keratinised layer (stratum corneum) made up of horny scales, resists normal wear and tear and protects from injury.
The Keratinised layer is shed sloughed every 60-70 days or earlier or 3-4 times a year. In young ones and some species the rate of casting may be higher or only once in a year.
The snake, normally hiding just before casting, is lethargic. New epidermis is grown beneath the old skin and secretes a thin layer of fluid between old and new skin. The fluid secretion makes the snake almost if not completely blind.
Shedding starts by opening and stretching the mouth and rubbing it on surrounding available objects until the old skin at the edges of lips begins to split. The process of rubbing continues till the skin is shed in one piece from head to tail or some times the skin will break up and come off in pieces.
The skin, turned inside out like a tight glove being pulled off from hand, is a perfect cast of the snake including eye scales. This process takes nearly half an hour or more.
The cast is completely devoid of colour as the pigment cells remain in the dermis which is never shed. The shedded skin is transparent and brittle. After casting the snake becomes fresh, alert, active and bright. The sloughting indicates growth of snake and it is affected by factors such as health, environmental temperature and amount of food taken.
Published in The Hindu on Jan 31, 2002.