question: Why do snakes shed their skin?
comment: The reason shedding skin is advantageous in their evolution is many-fold: 1. Their skin - like ours - can't grow other than through creating new cells. So...they shed it to make way for new skin that fits their growing body. 2. skin is the "outer layer" - it gets hurt/damaged etc. by shedding it you get a fresh set of armor. 3. Snakes live in a feast-or-famine world. Humans can be constantly shedding and recreating, but by doing it all at once, it can be timed with energy availability (which also corresponds to when growth occurs).
passages: Molting, or ecdysis, serves a number of functions. Firstly, the old and worn skin is replaced; secondly, it helps get rid of parasites such as mites and ticks. Renewal of the skin by molting is supposed to allow growth in some animals such as insects; however, this has been disputed in the case of snakes.
   The shedding of scales is called "ecdysis" (or in normal usage, "molting" or "sloughing"). In the case of snakes, the complete outer layer of skin is shed in one layer. Snake scales are not discrete, but extensions of the epidermis—hence they are not shed separately but as a complete outer layer during each molt, akin to a sock being turned inside out.
   The molting of the skin occurs regularly in snakes. This is when old skin is outgrown. In the case of snakes, it is called "shedding" or "ecdysis." Snakes will rub against rough surfaces to shed their skin. A shed skin is much longer than the snake that shed it, as the skin covers the top and bottom of each scale. If the skin is shed intact, each scale is unwrapped on the top and bottom side of the scale which almost doubles the length of the shed skin. While a snake is in the process of shedding the skin over its eye, the eye may become milky. This impairs the vision of the snake and may result in aggressive behavior.
   Shedding. Reptiles shed their skin through a process called ecdysis which occurs continuously throughout their lifetime. In particular, younger reptiles tend to shed once every 5–6 weeks while adults shed 3–4 times a year. Younger reptiles shed more because of their rapid growth rate. Once full size, the frequency of shedding drastically decreases. The process of ecdysis involves forming a new layer of skin under the old one. Proteolytic enzymes and lymphatic fluid is secreted between the old and new layers of skin. Consequently, this lifts the old skin from the new one allowing shedding to occur. Snakes will shed from the head to the tail while lizards shed in a “patchy pattern”. Dysecdysis, a common skin disease in snakes and lizards, will occur when ecdysis, or shedding, fails. There are numerous reasons why shedding fails and can be related to inadequate humidity and temperature, nutritional deficiencies, dehydration and traumatic injuries. Nutritional deficiencies decrease proteolytic enzymes while dehydration reduces lymphatic fluids to separate the skin layers. Traumatic injuries on the other hand, form scars that will not allow new scales to form and disrupt the process of ecdysis.
   In the case of snakes, the complete outer layer of skin is shed in one layer. Snake scales are not discrete but extensions of the epidermis hence they are not shed separately, but are ejected as a complete contiguous outer layer of skin during each moult, akin to a sock being turned inside out. Moulting is repeated periodically throughout a snake's life. Before a moult, the snake stops eating and often hides or moves to a safe place. Just prior to shedding, the skin becomes dull and dry looking and the eyes become cloudy or blue-colored. The old skin breaks near the mouth and the snake wriggles out, aided by rubbing against rough surfaces. In many cases the cast skin peels backward over the body from head to tail, in one piece like an old sock. A new, larger, and brighter layer of skin has formed underneath.
   Moulting serves a number of functions – firstly, the old and worn skin is replaced, secondly, it helps get rid of parasites such as mites and ticks. Renewal of the skin by moulting is supposed to allow growth in some animals such as insects, however this view has been disputed in the case of snakes.
   Molting occurs periodically throughout the snake's life. Before a molt, the snake stops eating and often hides or moves to a safe place. Just before shedding, the skin becomes dull and dry looking and the eyes become cloudy or blue-colored. The inner surface of the old skin liquefies. This causes the old skin to separate from the new skin beneath it. After a few days, the eyes clear and the snake "crawls" out of its old skin. The old skin breaks near the mouth and the snake wriggles out, aided by rubbing against rough surfaces. In many cases, the cast skin peels backward over the body from head to tail in one piece, like pulling a sock off inside-out. A new, larger, brighter layer of skin has formed underneath.
   The shedding of scales is called "ecdysis", or, in normal usage "moulting" or "sloughing". In the case of snakes, the complete outer layer of skin is shed in one layer. Snake scales are not discrete but extensions of the epidermis hence they are not shed separately, but are ejected as a complete contiguous outer layer of skin during each moult, akin to a sock being turned inside out.
   Crested geckos shed their skin up to once a week when young. When fully grow, the process only occurs once every one or two months.
   Section::::Skin of a living snake.:Structures and function.:Molting.
  
  Molting is common, and results in the entire outer layer of epidermis being lost. For more about molting, see the Snake page. For more about the epidermal scales of the snake, see the Snake scale page.
  
  Section::::Skin of a living snake.:Structures and function.:Protection and friction reduction.
   The most familiar example of moulting in reptiles is when snakes "shed their skin". This is usually achieved by the snake rubbing its head against a hard object, such as a rock (or between two rocks) or piece of wood, causing the already stretched skin to split. At this point, the snake continues to rub its skin on objects, causing the end nearest the head to peel back on itself, until the snake is able to crawl out of its skin, effectively turning the moulted skin inside-out. This is similar to how one might remove a sock from one's foot by grabbing the open end and pulling it over itself. The snake's skin is often left in one piece after the moulting process, including the discarded brille (ocular scale), so that the moult is vital for maintaining the animal's quality of vision. The skins of lizards, in contrast, generally fall off in pieces.
   Moulting serves a number of functions - first, the old and worn skin is replaced; second, it helps get rid of parasites such as mites and ticks. Renewal of the skin by moulting is supposed to allow growth in some animals such as insects, however this view has been disputed in the case of snakes.
  
  In the case of lizards, this coating is shed periodically, usually coming off in flakes, but in some cases, such as lizards having elongated bodies, in a single piece. Some geckos will eat their own shed skin.
   Moulting is repeated periodically throughout a snake's life. Before a moult, the snake stops eating and often hides or moves to a safe place. Just before shedding, the skin becomes dull and dry looking and the eyes become cloudy or blue-colored. The inner surface of the old outer skin liquefies. This causes the old outer skin to separate from the new inner skin. After a few days, the eyes clear and the snake "crawls" out of its old skin. The old skin breaks near the mouth and the snake wriggles out aided by rubbing against rough surfaces. In many cases the cast skin peels backward over the body from head to tail, in one piece like an old sock. A new, larger, and brighter layer of skin has formed underneath.
   An older snake may shed its skin only once or twice a year. But a younger snake, still growing, may shed up to four times a year. The discarded skin gives a perfect imprint of the scale pattern, and it is usually possible to identify the snake if the discarded skin is reasonably intact. This periodic renewal has led to the snake being a symbol of healing and medicine, as pictured in the Rod of Asclepius.
   "M. moilensis" will shed once every 30–50 days. Like other snakes, the process will take about 7–10 days. On the first two days, the eyes will become bluish in color and the skin will become pale. A week later, the snake will shed its skin. During the whole period, you should avoid handling the snake or feeding it.
   Section::::Skin of a living snake.:Structures and function.:Permeability.
  
  Skin permeability may change seasonally in snakes to help with the problem of drying out. It is known that desert snakes have generally impermeable skins, and that aquatic snakes have a more permeable skin that can sometimes trap water to prevent drying out. Some snakes may change their environment throughout the year, and may subsequently change their skin's permeability as a result. For instance, aquatic snakes may latch on to more water if they are in an environment that is drying out by attracting a layer of water under their scales.
   When they shed their skin, they bloat themselves and make a coughing sound, then start to tear the old skin off with their mouth, and eat it for nutrition, to reveal newer, brighter skin.
  
  Section::::Diet.
   Those found in the wild typically have more dark, dull, and drab colorations than those kept in captivity as pets. Those in captivity generally have an assortment of skin colors and patterns. The skin of a common leopard gecko is very durable, which provides protection from the rough sand and rocky hills terrain of their dry environment. Their dorsal side is covered with small bumps, which gives a rough texture and appearance while their ventral side is thin, transparent, and smooth. Like all reptiles, common leopard geckos shed their skin. In the few days before the shedding, the skin will turn color to a translucent whitish gray. Adults shed an average of once a month, while juveniles will sometimes shed twice as much. The gecko will eat its old skin after shedding, revealing a brighter colored one. There are two theories of why common leopard geckos do this. One is that in the wild, common leopard geckos eat their shed skin so there is no trace that the common leopard gecko was there. The other theory is that eating the shed skin is a means for obtaining protein and other vitamins for growth.
   An older snake may shed its skin only once or twice a year, but a younger, still-growing snake, may shed up to four times a year. The discarded skin gives a perfect imprint of the scale pattern and it is usually possible to identify the snake if this discard is reasonably complete and intact.
  
  Section::::Arrangement of scales.
  
  Scale arrangements are important, not only for taxonomic utility, but also for forensic reasons and conservation of snake species.
   Section::::Biology.:Skin.
  
  The skin of a snake is covered in scales. Contrary to the popular notion of snakes being slimy because of possible confusion of snakes with worms, snakeskin has a smooth, dry texture. Most snakes use specialized belly scales to travel, gripping surfaces. The body scales may be smooth, keeled, or granular. The eyelids of a snake are transparent "spectacle" scales, which remain permanently closed, also known as brille.
   This species was heavily hunted for their hides. In 1970 they were provided protection and the export of their skin dropped. Now local populations are safe where their habitat is protected. Captive farms have since been set up to provide animals for the leather trade. In recent years a number of these animals have found themselves in the pet trade.
  
  Section::::Habits.
   Third, the scales in lepidosaurs are horny (keratinized) structures of the epidermis, allowing them to be shed collectively, contrary to the scutes seen in other reptiles. This is done in different cycles, depending on the species. However, lizards generally shed in flakes while snakes shed in one piece. Unlike scutes, lepidosaur scales will often overlap like roof tiles.
  
  Section::::General description.
   The ringed caecilian ("Siphonops annulatus") has developed a unique adaptation for the purposes of reproduction. The progeny feed on a skin layer that is specially developed by the adult in a phenomenon known as maternal dermatophagy. The brood feed as a batch for about seven minutes at intervals of approximately three days which gives the skin an opportunity to regenerate. Meanwhile, they have been observed to ingest fluid exuded from the maternal cloaca.
  
  Section::::Life cycle.:Parental care.
   Reptiles, including snakes, possess extensive keratinization of the epidermis in the form of epidermal scales. A snake's epidermis is composed of four layers. The outer layer of a snake's skin is shed periodically, and is therefore a temporary layer, and is highly keratinized. Beneath the outer layer is the corneal layer (stratum corneum), which is thickened and flexible. Under the corneal layer is intermediary zone (stratum granulosum) and the basal layer (stratum basale), respectively. The dermis of a snake resides beneath the epidermis. The dermis of snakes is generally fibrous in nature, and not very prominent.The dermis houses pigment cells, nerves, and collagen fibers. Nerve fibers extend into the snake epidermis and anchor near scales, generally at the rostral, or head, end of the snake. Specifically, nerves anchor to sensory spines and pits, which are touch and thermal detection organs, respectively. The hypodermis is below the dermis. This layer mainly stores fat. 
   An important function of the skin is the sensation of changes in air temperature, which can guide the snakes towards warm basking/shelter locations. All snakes are ectotherms. To maintain a stable body temperature, they exchange heat with their external environments. Snakes often move into open, sunny areas to absorb heat from the sun and warmed earth, a behavior known as basking. Nerves in the skin regulate the flow of blood into the veins near the surface. Rubio states, "The skin's acceptance of radiant energy, its ability to determine the temperature, and the snake's ability to move toward or away from one temperature gradient to another are among the most important behavioral actions in its daily life."
  