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, like other , have skin covered in scales.Boulenger, George A. 1890 The Fauna of British India. p. 1 Snakes are entirely covered with scales or of various shapes and sizes, known as snakeskin as a whole. A scale protects the body of the snake, aids it in locomotion, allows moisture to be retained within, alters the surface characteristics such as roughness to aid in camouflage, and in some cases even aids 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 The Snakes of Indiana at The Centre for Reptile and Amphibian Conservation and Management, Indiana. Retrieved 14 August 2006. 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.
Snakes have smaller scales around the mouth and sides of the body which allow expansion so that a snake can consume prey of much larger width than itself. Snake scales are made of keratin, the same material that hair and fingernails are made of. They are cool and dry to touch. Herpetology FAQ at San Diego Museum of Natural History. Retrieved 14 August 2006.
Certain primitive snakes such as Boidae, Pythonidae and certain advanced snakes such as Viperidae have small scales arranged irregularly on the head. Other more advanced snakes have special large symmetrical scales on the head called shields or plates.
Snake scales occur in variety of shapes. They may be cycloid as in family Typhlopidae,Boulenger, George A. The Fauna of British India... page 234 long and pointed with pointed tips, as in the case of the green vine snake Ahaetulla nasuta,Smith, Vol III, p. 6 broad and leaf-like, as in the case of green pit vipers Trimeresurus spp. or as broad as they are long, for example, as in rat snake Ptyas mucosus. In some cases, scales may be keeled scales weakly or strongly as in the case of the buff-striped keelback Amphiesma stolatum. They may have bidentate tips as in some spp of Natrix. Some snakes, such as the short seasnake Hydrophis curtus, may have spinelike and juxtaposed scales while others may have large and non-overlapping knobs as in the case of the Javan mudsnake Xenodermus javanicus.
Another example of differentiation of snake scales is a transparent scale called the brille or spectacle which covers the eye of the snake. The brille is often referred to as a fused eyelid. It is shed as part of the old skin during .
Some snakes have the ability to change the hue of their scales slowly. This is typically seen in cases where the snake becomes lighter or darker with change in season. In some cases, this change may take place between day and night.
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 is supposed to allow growth in some animals such as insects, however this view has been disputed in the case of snakes. ZooPax Scales Part 3. Whozoo.org. Retrieved on 2013-01-21.
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. General Snake Information. Division of Wildlife, South Dakota
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.
The dorsal (or body) scales on the snake's body are arranged in rows along the length of their bodies. Adjacent rows are diagonally offset from each other. Most snakes have an odd number of rows across the body though certain species have an even number of rows e.g. Zaocys spp. In the case of some aquatic and marine snakes, the scales are granular and the rows cannot be counted.
The number of rows range from ten in Tiger Ratsnake Spilotes pullatus; thirteen in Lycodon, Liopeltis, Calamaria and Asian coral snakes of genus Calliophis; 65 to 75 in Pythonidae; 74 to 93 in Kolpophis and 130 to 150 in Acrochordus. The majority of the largest family of snakes, the Colubridae have 15, 17 or 19 rows of scales.Smith, Vol III, p. 7 The maximum number of rows are in mid-body and they reduce in count towards the head and on the tail.
The scales around the eye are called circumorbital scales and are named as ocular scales but with appropriate prefixes. The ocular scale proper is a transparent scale covering the eye which is called the spectacle, brille or eyecap.. Arachnophiliac.co.uk (2007-02-12). Retrieved on 2013-01-21. The circumorbital scales towards the snout or the front are called preocular scales, those towards the rear are called postocular scales, and those towards the upper or dorsal side are called supraocular scales. Circumorbital scales towards the ventral or lower side, if any, are called subocular scales. Between the preocular and the postnasal scales are one or two scales called loreal scales. Loreal scales are absent in elapids.
The scales along the lips of the snake are called labials. Those on the upper lip are called supralabials or upper labials, while those on the lower lip are called infralabials or lower labials. On top of the head, between the eyes, adjacent to the supraoculars is the frontal scale. The prefrontal scales are the scales connected to the frontal towards the tip of the snout which are in contact with the internasals. They may have a scale in between them. The back of the top of the head has scales connected to the frontal scale called the parietal scales. At the sides of the back of the head between the parietals above and the supralabials below are scales called temporal scales.
On the underside of the head, a snake has an anterior scale called the mental scale. Connected to the mental scale and all along the lower lips are the infralabials or lower labials. Along the chin connected to the infralabials is a pair of shields called the anterior chin shields. Next to the anterior chin shields, further back along the chin is another pair of shields called the posterior chin shields. In some texts the chinshields are referred to as submaxillary scales.
Scales in the central or throat region, which are in contact with the first ventral scales of a snake's body and are flanked by the chin shields, are called gular scales. The mental groove is a longitudinal groove on the underside of the head between the large, paired chin shields and continuing between the smaller gular scales.
Sometimes snakes have enlarged scales, either single or paired, under the tail; these are called subcaudals or urosteges. These subcaudals may be smooth or keeled as in Bitis arietans somalica. The end of the tail may simply taper into a tip (as in the case of most snakes), it may form a spine (as in Acanthophis), end in a bony spur (as in Lachesis), a rattle (as in Crotalus), or a rudder as seen in many sea snakes.
Details for this section have been sourced from scale diagrams in Malcolm Smith.Smith, Vol III, p. 29 Details of scales of Buff-striped Keelback have been taken from Daniels.Daniels, J.C. (2002). Book of Indian Reptiles and Amphibians. BNHS. Oxford University Press. Mumbai, pp. 116–118 .
In certain areas in North America, where the diversity of snakes is not too large, easy keys based on simple identification of scales have been devised for the lay public to distinguish venomous snakes from non-venomous snakes. North Carolina State Wildlife Damage Notes – Snakes . Ces.ncsu.edu. Retrieved on 2013-01-21. Pennsylvania State University – Wildlife Damage Control 15 (pdf) . (PDF) . Retrieved on 2013-01-21. In other places with large biodiversity, such as Myanmar, publications caution that venomous and non-venomous snakes cannot be easily distinguished apart without careful examination.
The scales patterning may also be used for individual identification in field studies. Clipping of specific scales, such as the subcaudals, to mark individual snakes is a popular approach to population estimation by mark and recapture techniques.Resources Inventory Branch, Ministry of Environment, Lands and Parks Resources Inventory Branch for the Terrestrial Ecosystems Task Force Resources Inventory Committee . (1998). Inventory Methods for Snakes Standards for Components of British Columbia's Biodiversity No. 38 .
Species identification using scales requires a fair degree of knowledge about snakes, their taxonomy, snake-scale nomenclature as well as familiarity with and access to scientific literature. Distinguishing by using scale diagrams whether a snake is venomous or not in the field cannot be done in the case of uncaught specimens. It is not advisable to catch a snake to check whether it is venomous or not using scale diagrams. Most books or websites provide an array of traits of the local herpetofauna, other than scale diagrams, which help to distinguish whether a snake in the field is venomous or not. How To Identify Snakes. kentuckysnakes.org.Berger, Cynthia. (2007). Venomous Snakes. Stackpole books. .
In certain regions, presence or absence of certain scales may be a quick way to distinguish non-venomous and venomous snakes, but used with care and knowledge of exceptions. For example, in Myanmar, the presence or absence of can be used to distinguish between relatively harmless Colubrids and lethally venomous Elapids. The rule of hand for this region is that the absence of a loreal scale between the nasal scale and ocular scale indicates that the snake is an Elapid and hence lethal. This rule-of-thumb cannot be used without care as it cannot be applied to vipers, which have a large number of small scales on the head. A careful check would also be needed to exclude known poisonous members of the Colubrid family such as Rhabdophis.
In South Asia, it is advisable to take the snake which has bitten a person, if it has been killed, and carry it along to the hospital for possible identification by medical staff using scale diagrams so that an informed decision can be taken them as to whether and which anti-venom is to be administered. However, attempts to catch it or kill the venomous snake are not advised as the snake may bite more people.Directorate General Armed Forces Medical Services, India. Memorandum No 102 : Snakebite. Undated.pdf available . Accessed on 21 Feb 2010.
Snakeskin, with its highly periodic cross-hatch or grid patterns, appeals to people's aesthetics and have been used to manufacture many leather articles including fashionable accessories.Voland, Eckart and Grammer, Karl (2003) Evolutionary Aesthetics, Springer, pp. 108–116 . The use of snakeskin has however endangered snake populations The Endangered Species Handbook – Trade (chapter) Reptile Trade – Snakes and Lizards (section) – accessed on 15 August 2006 and resulted in international restrictions in trade of certain snake species and populations in the form of CITES provisions. Species in Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) – accessed on 14 August 2006 Animal lovers in many countries now promote the use of artificial snakeskin instead, which are easily produced from embossed leather, patterned fabric, plastics and other materials.
Snake scales occur as a motif regularly in PC game. Gabriel Knight – Sins of the Father. Gameboomers.com. Retrieved on 2013-01-21. Snake Rattle 'n Roll. consoleclassix.com. Retrieved on 2013-01-21. Allahkazam's Magical Realm. Everquest.allakhazam.com. Retrieved on 2013-01-21. Monsters/Pets : Reptile. Legend of Mana. qrayg.com A snake scale was portrayed as a clue in the 1982 film Blade Runner. Encyclopaedia. Brmovie.com. Retrieved on 2013-01-21. Snake scales also figure in popular fiction, such as the Harry Potter series (desiccated Boomslang skin is used as a raw material for concocting the Polyjuice Potion), and also in teen fiction.Quynh-Nhu, Daphne (April 2006). Jade Green and Jade White. teenink.com. Retrieved on 2013-01-21.
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