The presence of scales is a fundamental characteristic of snakes. Scales are an integral part of the snake’s anatomy, distinguishing them from other animal classes. This unique integumentary system allows the snake to thrive across diverse and often challenging global environments. Every snake species relies on this specialized skin structure for survival.
The Universal Presence of Scales
Every portion of a snake’s body is covered by scales, forming a continuous, protective sheet. Unlike popular misconceptions that often portray snakes as slimy, their scales are completely dry to the touch. This dry, overlapping covering separates reptiles from amphibians, whose skin must remain moist to facilitate breathing. The entire collection of scales, often called the snakeskin, is a single, cohesive unit. There are no exceptions to this rule among the thousands of known snake species.
Physical Structure and Composition
Snake scales are formed from the epidermis, the outermost layer of the skin, and are composed primarily of a tough, fibrous protein called keratin. This protein is specialized into two forms: pliable alpha-keratin and rigid beta-keratin. The beta-keratin provides the hardness and structural integrity to the scale’s outer surface. These structures are not separate plates but rather folds in the skin, with each scale overlapping the next like shingles on a roof.
The body features two main types of scales that differ in size and function. The dorsal scales, which cover the back and sides, can be either smooth or keeled, meaning they possess a raised ridge down the center. Covering the underside are the specialized ventral scales. These are noticeably larger, wider, and arranged in a single row across the snake’s belly, where they are crucial for movement and traction.
How Scales Aid Survival
The scales provide multiple functional benefits, beginning with mechanical protection against abrasion and injury. As a snake moves across rough terrain, the tough keratin layer shields the underlying skin and tissue. This armor also serves as a defense against minor attacks and helps to deter predators.
The ventral scales are specifically adapted to facilitate efficient locomotion, acting like the treads on a tire. The rough edges of these scutes grip tiny imperfections on surfaces, allowing the snake to push itself forward and climb with ease. This frictional property is important for terrestrial movement, minimizing energy lost to sliding.
Scales also play a role in moisture regulation, preventing excessive water loss through evaporation. This adaptation is important for species inhabiting arid environments, effectively sealing the body and retaining hydration. Finally, the patterns and colors that provide camouflage or aposematic (warning) displays are held within the scales.
The Cycle of Scale Replacement
Because the scales are rigid, they cannot grow larger as the snake matures, necessitating replacement. This shedding of the entire outer layer of skin is known as ecdysis, a recurring necessity that allows for growth and health maintenance. Younger snakes, which are rapidly increasing in size, may undergo ecdysis more frequently than older individuals.
The process begins when a new layer of skin forms underneath the old epidermal layer. Fluid, including lymph, is secreted between the two layers, causing the old skin to separate and the outer layer to appear dull and cloudy, particularly over the eyes.
After a few days, the snake will rub its head against rough objects to initiate a tear, usually near the lip. A healthy shed typically results in the old skin being peeled off in one continuous piece. This mechanism also serves the function of ridding the animal of external parasites and healing minor surface damage.