Snake scales

Snakes, like other reptiles, have a skin covered in a scale. Snakes are entirely covered with a scale or scutes of various shapes and sizes, known as snakeskin as a whole. A scale protect the body of the snake, aid it in locomotion, allow moisture to be retained within, alter the surface characteristics such as roughness to aid in camouflage, and in some cases even aid in prey capture (such as Acrochordus). The simple or complex colouration patterns (which help in camouflage and anti-predator display) are a property of the underlying skin, but the folded nature of scaled skin allows bright skin to be concealed between scales then revealed in order to startle predators.

Scales have been modified over time to serve other functions such as 'eyelash' fringes, and protective covers for the eyes with the most distinctive modification being the rattle of the North American rattlesnakes.

Snakes periodically moult their scaly skins and acquire new ones. This permits replacement of old worn out skin, disposal of parasites and is thought to allow the snake to grow. The arrangement of scales is used to identify snake species.

Snakes have been part and parcel of culture and religion. Vivid scale patterns have been thought to have influenced early art. The use of snake-skin in manufacture of purses, apparel and other articles led to large-scale killing of snakes, giving rise to advocacy for use of artificial snake-skin. Snake scales are also to be found as motifs in fiction, art and films.

The scales of a snake primarily serve to reduce friction as it moves, since friction is the major source of energy loss in snake locomotion.

The ventral (or belly) scales, which are large and oblong, are especially low-friction, and some arboreal species can use the edges to grip branches. Snake skin and scales help retain moisture in the animal's body. Snakes pick up vibrations from both the air and the ground, and can differentiate the two, using a complex system of internal resonances (perhaps involving the scales).

Reptiles evolved from amphibious ancestors which left the aquatic lifestyle and became terrestrial. To prevent loss of moisture reptilian skin lost the softness and moisture of amphibian skin and developing a thick stratum corneum with multiple layers of lipids which served as an impermeable barrier as well as provided protection from the ultraviolet. Over time, reptilian skin cells became highly keratinised, horny, sturdy and desiccated. The surfaces of the dermis and epidermis of all reptilian scales form a single contiguous sheet, as can be seen when the snake sheds its skin as a whole.

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