Snakes!
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An old synonym for snake is serpent (which comes from Old French, and ultimately from *serp-, "to creep"); in modern usage this usually refers to a mythic or symbolic snake, and information about such creatures will be found under serpent (symbolism). This article deals with the biology of snakes.
Snake Evolution
The phylogeny of snakes is poorly known due to the fact that snake skeletons are typically small and fragile, making fossilization unlikely. It has however been generally agreed, on the basis of morphology, that snakes descended from lizard-like ancestors. Recent research based on genetics and biochemistry confirms this; snakes form a venom clade with several extant lizard families.Recent fossil evidence suggests that snakes directly evolved from burrowing lizards, either varanids or some other group. An early fossil snake, Najash rionegrina, was a two-legged burrowing animal with a sacrum, fully terrestrial. One extant analog of these putative ancestors is the earless monitor Lanthanotus of Borneo, although it also is semi-aquatic. As these ancestors became more subterranean, they lost their limbs and became more streamlined for burrowing. Features such as the transparent, fused eyelids and loss of external ears, according to this hypothesis, evolved to combat subterranean conditions (scratched corneas, dirt in the ears). According to this hypothesis, snakes re-emerged onto the surface of the land much as they are today. Other primitive snakes are known to have possessed hindlimbs but lacked a direct connection of the pelvic bones to the vertebrae, including Haasiophis, Pachyrhachis and Eupodophis) which are slightly older than Najash.
Modern boas do have vestigal hind limbs, tiny, clawed digits known as anal spurs and used to grasp during mating.
The alternative hypothesis, based on morphology, suggests that ancestors were related to mosasaurs extinct aquatic reptiles from the Cretaceous which in turn are thought to have derived from varanid lizards. Under this hypothesis, the fused, transparent eyelids of snakes are thought to have evolved to combat marine conditions (corneal water loss through osmosis), while the external ears were lost through disuse in an aquatic environment, ultimately leading to an animal similar in appearance to sea snakes of today. In the Late Cretaceous, snakes re-colonized the land much like they are today. Fossil snake remains are known from early Late Cretateous marine sediments, which is consistent with this hypothesis, particularly as they are older than the terrestrial Najash rionegrina. Similar skull structure; reduced/absent limbs; and other anatomical features found in both mosasaurs and snakes lead to a positive cladistical correlation, though some features are also shared with varanids. Supposedly similar locomotion for both groups is also used as support for this hypothesis. Genetic studies have indicated that snakes are not especially related to monitor lizards, and (it has been claimed) therefore not to mosasaurs, the proposed ancestor in the aquatic scenario of their evolution. However, there is more evidence linking mosasaurs to snakes than to varanids. Fragmentary remains that have been found from the Jurassic and Early Cretaceous indicate deeper fossil records for these groups, which may eventually refute either hypothesis.
The great diversity of modern snakes appeared in the Paleocene, probably correlated with the adaptive radiation of mammals following the extinction of the dinosaurs.
Snake Feeding
It has been suggested that Snake food be merged into this article or section.Snake eating a mouseAll snakes are carnivorous, eating small animals including lizards and other snakes, rodents and other small mammals, birds, eggs or insects. Some snakes have a venomous bite which they use to kill their prey before eating it. Other snakes kill their prey by constriction. Still others swallow their prey whole and alive. Read more about snake food.
Snakes do not chew their food and have a very flexible lower jaw, the two halves of which are not rigidly attached, and numerous other joints in their skull (see snake skull), allowing them to open their mouths wide enough to swallow their prey whole, even if it is larger in diameter than the snake itself. It is a common misconception that snakes actually dislocate their lower jaw to consume large prey.
After eating, snakes become torpid while the process of digestion takes place. Digestion is an intensive activity, especially after the consumption of very large prey. In species which feed only sporadically, the entire intestine enters a reduced state between meals to conserve energy, and the digestive system is 'up-regulated' to full capacity within 48 hours of prey consumption. So much metabolic energy is involved in digestion that in Crotalus durissus, the Mexican rattlesnake, an increase of body temperature to as much as 14 degrees Celsius above the surrounding environment has been observed. Because of this, a snake disturbed after having eaten recently will often regurgitate its prey in order to be able to escape the perceived threat. However, when undisturbed, the digestive process is highly efficient, dissolving and absorbing everything but hair and claws, which are excreted along with uric acid waste. Snakes have been known to occasionally die from trying to swallow an animal that is too big. Snake digestive acids are unable to digest most plant matter, which passes through the digestive system mostly untouched.
Snakes do not normally prey on people, but there are instances of small children being eaten by large constrictors in the jungle. While some particularly aggressive species exist, most will not attack humans unless startled or injured, preferring instead to avoid contact. The majority of snakes are either non-venomous or possess venom that is not harmful to humans.
Snake Skin
The skin is covered in scales. Most snakes use specialized belly scales to move, gripping surfaces. The body scales may be smooth, keeled, or granular. Their eyelids are transparent "spectacle" scales which remain permanently closed. They shed their skin periodically. Unlike other reptiles, this is done in one piece, like pulling off a sock. The primary purpose of this is to grow; shedding also removes external parasites. This periodic renewal has led to the snake being a symbol of healing and medicine, as pictured in the Rod of Asclepius. In "advanced" (Caenophidian) snakes, the broad belly scales and rows of dorsal scales correspond to the vertebrae, allowing scientists to count the vertebrae without dissection. If there is not enough humidity in the air while snakes are shedding their skin, it can be very dangerous for the snake, because the dry skin does not shed. Skin that remains attached to the snake can harbour diseases and parasites. A tail tip that is not removed can constrict as the snake grows, cutting off the blood supply to the end of the tail causing it to drop off. A retained spectacle can cause the snake to become blind in the affected eye.Snake Perception
While snake vision is unremarkable (generally being best in arboreal species and worst in burrowing species), it is able to detect movement. Some snakes, like the Asian vine snake, have binocular vision. In most snakes, the lens moves back and forth within the eyeball to focus. In addition to their eyes, some snakes (pit vipers, pythons, and some boas) have infrared-sensitive receptors in deep grooves between the nostril and eye which allow them to "see" the radiated heat.Snakes have no external ears, but they do have a bone called the quadrate under the skin on either side of the head which focuses sound into the cochlea. Their sense of hearing is most sensitive to frequencies around 200'300 Hz.
A snake smells by using its forked tongue to collect airborne particles then passing them to the Jacobson's organ in the mouth for examination. The fork in the tongue gives the snake a sort of directional sense of smell. The part of the body which is in direct contact with the surface of the ground is very sensitive to vibration, thus a snake is able to sense other animals approaching.
Snake Internal organs
The left lung is very small or sometimes even absent, as snakes' tubular bodies require all of their organs to be long and thin. To accommodate them all, only one lung is functional. This lung contains a vascularized anterior portion and a posterior portion which does not function in gas exchange. This 'saccular lung' may be used to adjust buoyancy in some aquatic snakes and its function remains unknown in terrestrial species. Also, many organs that are paired, such as kidneys or reproductive organs, are staggered within the body, with one located ahead of the other. The most primitive snakes, including boas and pythons, have anal spurs, a pair of claws on either side of the cloaca which are used by the males for stimulation of females during mating.Snake Locomotion
Snakes utilize a variety of methods of movement which allows them substantial mobility in spite of their legless condition. All snakes are capable of lateral undulation, in which the body is flexed side-to-side, and the flexed areas propagate posteriorly, giving the overall shape of a posteriorly propagating sine wave. In addition, all snakes are capable of concertina movement. This method of movement can be used to both climb trees and move through small tunnels. In the case of trees, the branch is grasped by the posterior portion of the body, while the anterior portion is extended. The anterior portion then grasps the branch, and the posterior portion is pulled forward. In the case of tunnels, instead of grasping, the body loops are pressed against the tunnel walls to attain traction, but the motion is otherwise similar. Another common method of locomotion is rectilinear locomotion, in which the snake remains straight and propels itself via a caterpillar-like motion of its belly-muscles. This mode is usually only used by very large, heavy snakes, such as large pythons and vipers. The most complex and interesting mode is sidewinding, an undulatory motion used to move across slippery mud or loose sand.Not all snakes dwell on land; sea snakes live in shallow tropical seas.
Studies of the motion and muscle activity of moving snakes have shed light on how each of these modes is achieved.
In terrestrial lateral undulation, posteriorly propagating unilateral waves of muscle contraction occur. The regions of muscle activity for each side extend from the most concave point on that side posteriorly to the most convex side. Thus, when a point on the snake's body is maximally flexed to the right, the right muscles activate, bending it back to the left until it's maximally right-convex, at which point the right side muscles turn off, and the left side muscles turn on. Speed is modulated primarily by alteration of frequency. Aquatic lateral undulation appears superficially similar, but the muscle activation pattern is different, with the regions of muscle activity being 'shifted' posteriorly to where they would be in terrestrial lateral undulation. The reasons for this difference are not fully understood.
Sidewinding, though it appears complex and confusing, is actually a simple modification of terrestrial lateral undulation. At the points of maximal flexion, the dorsalmost muscle group (traversospinalis group) activates, lifting that portion of the body over the ground, and resulting in other portions of the body remaining in static contact. This mode is used to cross slick surfaces such as mud flats and sand, and has nothing to do with thermoregulation, as is sometimes erroneously stated. Many species of snake, including species commonly kept as pets and which do not usually encounter deserts or mud flats, will sidewind when placed on a slick floor or tabletop and enticed to move fast.
Concertina locomotion and rectilinear locomotion are less well understood. Studies of muscle activity have only been done for tunnel concertina locomotion, which shows that the muscles are unilaterally active in static regions of bending in order to brace the snake against the tunnel walls. Rectilinear is believed to rely on different muscles from the other modes; while they all rely on the large epaxial muscles, rectilinear locomotion seems to rely upon the small costocutaneous muscles. However, this has not been verified experimentally, due to the difficulties in working with these small muscles.
"Flying" snakes
Several species of snake have the ability to glide, all being in the genus Chrysopelea. They are quite capable at it, able to travel as far as 137 metres through the air. They tend to make slithering motions to steer and help propel themselves along, propulsion being something unusual among the many gliding animals. This has contributed, in ancient times, to the belief in Wyrms (Legless, snake-like dragons that could supposedly fly.)Snake Reproduction
A wide range of reproductive modes are used by snakes. All snakes employ internal fertilization, accomplished by means of paired, forked hemipenes, which are stored inverted in the male's tail. Most snakes lay eggs, and of those most species abandon them shortly after laying; however, some species are ovoviviparous and retain the eggs within their bodies until they are almost ready to hatch. Recently, it has been confirmed that several species of snake are fully viviparous, nourishing their young through a placenta as well as a yolk sac, highly unusual among reptiles, or indeed anything else outside of placental mammals. Retention of eggs and live birth are commonly, but not exclusively, associated with cold environments, as the retention of the young within the female allows her to control their temperature more effectively than if the developing young were in external eggs.Snake bites
Documented deaths resulting from snake bites are uncommon in most areas of the world. Only about 450 species of snakes are venomous (with only about 250 that are able to kill a human), and among the 7,000 Americans bitten by venomous snakes every year, fewer than fifteen die (lightning kills more). See snakebites for more information, including prevention of snake bites and first aid treatment.Venomous snakes
A venomous snake is a snake that uses modified saliva, venom, delivered through fangs in its mouth, to immobilize or kill its prey. (In contrast, most non-venomous species are constrictors which suffocate their prey.) Venomous snakes include several families of snakes and do not constitute a formal classification group used in taxonomy.Venomous snakes are generally classified in four taxonomic families: Elapids - cobras, king cobras, kraits, mambas, copperheads, and coral snakes. Viperids - vipers, rattlesnakes, copperheads/cottonmouths, adders and bushmasters. Colubrids - boomslangs, tree snakes, vine snakes, mangrove snakes, and many others, though not all colubrids are venomous. Hydrophiidae - sea snakes. While about a quarter of snakes are venomous, not all such species are dangerous to humans. See snake venom. The following groups of snakes can be aggressive and inflict dangerous, even potentially lethal bites.
Brown Snake
American Copperhead
Asp Viper
Australian Copperhead
Bamboo Viper
Black Snake
Black Mamba
Boiga
Boomslang
Brown Snake (Australian)
Bushmaster
Common lancehead
Coral Snake
Cottonmouth
Death Adder
Eastern Diamondback Rattlesnake
Egyptian Cobra
Eyelash Viper
Fea's Viper
Fer-de-lance
Fierce Snake
Gaboon Viper
Green Mamba
King Cobra
Indian Cobra
Krait
Lancehead
Philippine Cobra
Rattlesnakes
Red Spitting cobra
Russell's Viper
Saw-scaled Viper
Sea Snakes
Sidewinder
Taipan
Tiger Snake
Urutu
Western Diamondback Rattlesnake
Although other snakes, such as pythons, do not have long fangs and are not venomous, their bites should still be attended to medically, because they often leave mouth bacteria and sometimes shed teeth in the bite.
Water moccasins
Agkistrodon piscivorus is a venomous pitviper species found in the eastern United States. Adults are large and capable of delivering a painful and potentially fatal bite, but their reputation for aggression is largely undeserved. This is the world's only semiaquatic viper, usually being found in or near water, particularly in slow-moving and shallow lakes and streams. The snake is a strong swimmer and will even enter the sea, successfully colonizing islands off both the Atlantic and Gulf coasts. Many of the common names refer to the fact that, when threatened, this species will often stand its ground and gape at an intruder, exposing the white lining of its mouth.The diet consists mainly of fish and frogs, but is otherwise highly varied and, uniquely, has even been reported to include carrion. The specific name is derived from the Latin words piscis and voro, which mean "fish" and "to eat"
Snakes as pets
Many varieties of snakes are docile and suitable as exotic pets.
Corn snake - 1.8 m
Rat snake - 1.8 m
King snake - 1.8 m
Milk snake - 0.9 m - various species
Red-tailed boa - 3.0 m to 3.6 m depending on species
Ball python - 1.8 m
Hognose snake - 0.9 m
Garter snakes - 0.9 m
Sand boa - 0.6 m
Blood python - 1.5 m
Burmese python over 6 m - largest docile snake, but not recommend for beginners due to size, strength and powerful feeding response.
"Beginner snakes" typically grow less than 180cm. Certain snakes are preferred as pets because they readily take food items that are inexpensive and acquired at many pet stores (feeder fish, crickets, small rodents, etc.) Some owners train their snakes to eat pre-killed meals (especially larger ones such as guinea pigs and rabbits) in order to avoid possible struggles with live prey leading to injuries to the snake, or out of sheer sympathy for the prey.
F/T refers to frozen/thawed food items. Some pet stores, such as PetSmart, only sell F/T feeders to avoid the perception of cruelty to the prey.
Snake charmers
A snake Charmer in Kochi, IndiaIn some parts of the world, especially in India and Pakistan, snake charming is a roadside show performed by a charmer. In this, the snake charmer carries a basket that contains a snake which he seemingly charms by playing tunes from his flute-like musical instrument, to which the snake responds. However, snakes' sense of hearing is not very sensitive to the range of the charmer's instrument, so they may not be able to hear the music at all. Researchers have pointed out that many of these snake charmers are good sleight-of-hand artists. The snake moves corresponding to the flute movement and the vibrations from the tapping of the charmer's foot which is not noticed by the public. They rarely catch their snakes and the snakes are either nonvenomous or defanged cobras. Sometimes these people exploit the fear of snakes by releasing snakes into the neighbourhood and then offering to rid the residence of snakes. Other snake charmers also have a snake and mongoose show, where both the animals have a mock fight; however, this is not very common, as the snakes, as well as the mongooses, may be seriously injured or killed.Snake trapping
Despite the existence of snake charmers, there have also been professional snake catchers or wranglers. The tribals of "Irulas" from Andhra Pradesh and Tamil Nadu in India have been practicising this art for generations. They generally don't use gimmicks and with the help of a simple stick catch the snakes from the fields or houses. They are also known to eat some of the snakes they catch and are very useful in rat extermination in the villages. Their knowledge of snakes and their behaviour is uncanny. Modern day snake trapping involves a herpetologist using a long stick with a "V" shaped end. Some like Steve Irwin prefer to catch them using bare hands.At least one tribe of natives uses a specialized form of snake catching as a rite of passage to manhood. The young man of interest will wrap his leg heavily in some type of cloth all the way to the inseam. He will then stick his leg in a burrow containing a large python, typically a reticulated python. After the snake swallows most of his leg several other members of the tribe will pull him out of the hole along with the snake. The snake is then killed and the man's leg removed from the snake. These snakes can be over 20 ft long and it is possible for the man to have his leg dislocated. The scent of a prey animal may be used to help convince to snake to swallow the leg.
Human consumption of snakes
In some cultures, the consumption of snakes is acceptable or even considered a delicacy, prized for its alleged pharmaceutical effect of warming the heart. Western cultures document the consumption of snake under extreme circumstances of hunger. However, human consumption of snake meat, especially when eaten raw, may lead to dangerous parasitic infections in humans. Rattlesnake meat is eaten in the western United States somewhat commonly. In Asian countries drinking the blood of snakes, particularly the cobra, is believed to increase sexual virility. The blood is drained while the cobra is still alive when possible, and is usually mixed with some form of liquor to improve the taste.Snake Symbolism
In Egyptian history, the snake occupies a primary role with the Nile cobra adorning the crown of the pharaoh in ancient times. It was worshipped as one of the Gods and was also used for sinister purposes: Murder of an adversary and ritual suicide (Cleopatra).In Greek Mythology snakes are often associated with deadly and dangerous antagonists. The 9 headed Hydra Hercules defeated and the three Gorgon sisters are literary examples. Medusa was one of the three Gorgon sisters who Perseus defeated. Medusa is described as a hideous mortal, with snakes instead of hair and the power to turn men to stone with her gaze.
India is often called the land of snakes and is steeped in tradition regarding snakes. Snakes are worshipped as gods even today with many women pouring milk on snake pits (despite snakes' aversion for milk). The cobra is seen on the neck of Shiva and Vishnu is depicted often as sleeping only on a 7 headed snake. There are also several temples in India solely for cobras sometimes called Nagraj (King of Snakes) and it is believed that snakes are symbols of fertility. There is a Hindu festival called Nagpanchami each year on which day snakes are venerated and prayed to.
In Christianity the snake makes its infamous appearance in the first book (Genesis) of the Bible when a snake appears before the first couple Adam and Eve and tempts them with the forbidden fruit. It is also seen in Exodus when Moses, as a sign of God's power, turns his stick into a snake to devour the pharaoh's snake. Later Moses made Nehushtan, a bronze snake on a pole that when looked at cured the people of bites from the snakes that plagued them in the desert. Jesus instucted his disciples to be be as shrewd as snakes and as innocent as doves.
The Ouroboros is a symbol that is associated with many different religions and customs, and is also claimed to be related to Alchemy. The Ouroboros or Oroboros is a snake manifesting it's own tail in a clock-wise direction (from the head to the tail) in the shape of a circle, representing manifestation of one's own life and rebirth, leading to immortality. The Ouroboros is also associated with the popular manga, Fullmetal Alchemist or Hagane no Renkinjutsushi by Dr. Kang's hero, Hiromu Arakawa.
Snake repellant
People will always try to sell you products, and magic cure-alls. Some products work, and some don't. In the field of wildlife control, you'll often find more bogus products than effective ones. Snakes are reptiles, not insects. The internet is full of snake deterrent products, but virtually none of them work. Some of these products include cinnamon or spicy powders, which is a nice idea in theory, but it isn't effective. Other products are simply made of napthalene - moth balls - which some companies sell as an end-all be-all in wildlife repellant. Sorry, it simply doesn't work. I've seen people dump a whole 5 lb. box of mothballs under a deck where snakes are living, and they don't care in the slightest. They keep using the area. People also claim that sulphur will keep snakes away. That is ridiculous. Hey, I know, why don't you just sprinkle lemon juice on the ground - that is sure to keep snakes at bay. Devices such as ultrasonic sound emitters that make a high-pitched noise are completely useless. I've been to so many properties over the years in which people have spent time and money on silly gimmicks like these, and then they hire a real wildlife control operator, and the problem is correctly taken care of.If you have a snake problem and you wish to get rid of them, they should be physically trapped and removed from the habitat. Either that, or physical barriers, such as fences (that go at least a foot underground) should be put in place as a means of snake prevention, to keep them from entering ground level areas.
Snake scales
Snakes, like other reptiles, have a skin covered in scales. Snakes are entirely covered with scales or scutes of various shapes and sizes. Scales 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, video games and films.
Functions of scales
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. Most snakes have at least some large scales (called 'shields') on their head, which can be used to distinguish different species. 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).
Snake scales are formed by the differentiation of the snake's underlying skin or epidermis. Each scale has an outer surface and an inner surface. The skin from the inner surface hinges back and forms a free area which overlaps the base of the next scale which emerges below this scale.
A snake hatches with a fixed number of scales. The scales do not increase in number as the snake matures nor do they reduce in number over time. The scales however grow larger in size and may change shape with each moult.
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.
Surface and shape of snake scales
Snake scales are of different shapes and sizes. Snake scales may be granular, have a smooth surface or have a longitudinal ridge or keel on it. Often, snake scales have pits, tubercles and other fine structures which may be visible to the naked eye or under a microscope. Snake scales may be modified to form fringes, as in the case of the Eyelash Bush Viper, Atheris ceratophora, or rattles as in the case of the rattlesnakes of North America.Certain primitive snakes such as boas, pythons and certain advanced snakes such as vipers have small scales arranged irregularly on the head. Other more advanced snakes have special large symmetrical scales on the head called shields or plates.
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 moulting.
Rattle scales
The most distinctive modification of the snake scale is the rattle of rattlesnakes, such as those of the genera Crotalus and Sistrurus. The rattle is made up of a series of loosely linked, interlocking chambers that when shaken, vibrate against one another to create the warning signal of a rattlesnake. Only the bottom button is firmly attached to the tip of the tail.At birth, a rattlesnake hatchling has only a small button or 'primordial rattle' which is firmly attached to the tip of the tail. The first segment is added when the hatchling sheds its skin for the first time. A new section is added each time the skin is shed until a rattle is formed. The rattle grows as the snake ages but segments are also prone to breaking off and hence the length of a rattle is not a reliable indicator of the age of a snake.
Scale Color
Scales, more specifically, mostly consist of hard beta keratins which are basically transparent. The colours of the scale are due to pigments in the inner layers of the skin and not due to the scale material itself. Scales are hued for all colours in this manner except for blue and green. Blue is caused by the ultrastructure of the scales. By itself, such a scale surface diffracts light and gives a blue hue, while, in combination with yellow from the inner skin it gives a beautiful iridescent green.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.
Scale Ecdysis
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.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.
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, 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.
Arrangement of snake scales
Excepting for the head, snakes have imbricate scales, overlapping like the tiles on a roof. Snakes have rows of scales along the whole or part of their length and also many other specialised scales, either singly or in pairs, occurring on the head and other regions of the body.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 Dryocalamus, Liopeltis, Calamaria and Asian coral snakes of genus Calliophis; 65 to 75 in pythons; 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.
The maximum number of rows are in mid-body and they reduce in count towards the head and on the tail.
Nomenclature of scales
The various scales on a snake's head and body are indicated in the following paragraphs with annotated photographs of Buff-striped Keelback Amphiesma stolata (a common grass-snake of South Asia).Head scales
Identification of scales is most conveniently begun with reference to the nostril which is easily identified on the snake. There are two scales enclosing the nostril which are called the nasals. The outer nasal (near the snout) is called the prenasal while the inner nasal (near the eye) is called the postnasal. Along the top of the snout connecting the nasals on both sides of the head are scales called internasals.Between the two prenasals is a scale at the tip of the snout called the rostral scale.
The scales around the eye are called circumorbital scales and are named as 'ocular' scales but with appropriate prefix. The ocular scale proper is a transparent scale covering the eye which is called the spectacle, brille or eyecap.
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 as supraocular scales. Circumorbital scales towards the ventral or lower side, if any, are called as subocular scales.
Between the preocular and the postnasal scales are the loreal scales.
The scales along the lips of the snake are called as labials. Those on the upper lip are called supralabials while those on the lower labial are called infralabials.
Between the eyeballs on top of the head, adjacent to the supraoculars are the frontal scales. The prefrontal scales are the scales connected to the frontals towards the tip of the snout which are in contact with the internasals.
The back of the top of the head has scales connected to the frontal scales called as the parietal scales. At the sides of the back of the head are scales called temporal scales.
On the underside of the head, a snake has an anterior scale called as the mental scale. Connected to the mental scales and all along the lower jaws are the infralabials. Along the lower jaw connected to infralabials are a pair of shields called the anterior chin shields. Next to the anterior chin shields, further back along the jaw are another pair of shields called the posterior chin shields.
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 large, paired chin shields and smaller gular scales.
Scales on the snake body
The scales on the body of the snake are called the dorsal or costal scales. Sometimes there is a special row of large scales along the top of the back of the snake, i.e, the uppermost row, called the vertebral scales.In "advanced" (Caenophidian) snakes, the broad belly scales and rows of dorsal scales correspond to the vertebrae, allowing scientists to count the vertebrae without dissection.
Tail scales
At the end of the ventral scales of the snake is an anal plate which protects the opening to the cloaca (a shared opening for waste and reproductive material to pass) on the underside near the tail. This anal scale may be single or divided into a pair. The part of the body beyond the anal scale is considered to be the tail.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.
Taxonomic importance
Scales do not play an important role in distinguishing between the families but are important at generic and specific level. There is an elaborate scheme of nomenclature of scales. Scales patterns, by way of scale surface or texture, pattern and colouration and the division of the anal plate, in combination with other morphological characteristics, are the principal means of classifying snakes down to species level.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 poisonous snakes from non-poisonous snakes. 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.
Identification of snakes by reference to scales seems an arcane art to the amateur naturalist because the nomenclature of snake scales seems esoteric and, more importantly, the snakes need to be caught and the head and body examined closely in hand for identification. The advent of high definition digital cameras means that images taken of snakes, if of appropriate definition and of the correct position, would show scales that can be examined, distinguished and counted without the need for catching and handling.
The scales patterning may also be used for individual identification in field studies. Clipping of specific scales to mark individual snakes is a popular approach to population estimation by mark and recapture techniques.
Distinguishing between venomous and non-venomous snakes
Finding out whether a snake is venomous or not is correctly done by identification of the species of a snake with the help of experts, or in their absence, close examination of the snake and using authoritative references on the snakes of the particular geographical region to identify it. Scale patterns help indicate the species and from the references, it can be verified if the snake species is venomous or not.A point to note is that such identification requires a fair degree of knowledge about snakes, their taxonomy, snake-scale nomenclature as well as familiarity and access to authoritative scientific texts on snakes.
In certain regions, experts use presence or absence of certain scales to distinguish between non-venomous and venomous scales, with well-understood exceptions. For example, in relation to venomous snakes of Myanmar, the distribution of snakes permits the use of the presence or absence of loreal scales 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 pre-ocular scale indicates that the snake is an Elapid and hence lethal.
Please note that this rule-of-hand applies to terrestrial venomous snakes only and that vipers are an exception since they cannot be so classified due to the large number of small scales on the head. Subsequently a further check is to be carried out in the case of identified Colubrids to exclude known poisonous members of their family such as Rhabdophis species.
In South Asia, it is advisable to kill the snake which has bitten a person 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-venin is to be administered.
Cultural significance of snake scales
Snakes have been a motif in human culture and religion and an object of dread and fascination all over the world. The vivid patterns of snake scales, such as the Gaboon Viper, both repel and fascinate the human mind. Such patterns have inspired dread and awe in humans from pre-historic times and these can be seen in the art prevalent to those times. Studies of fear imagery and psychological arousal indicate that snake scales are a vital component of snake imagery. Snake scales also appear to have affected Islamic art in the form of tessallated mosaic patterns which show great similarity to snake-scale patterns.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. The use of snakeskin has however endangered snake populations and resulted in international restrictions in trade of certain snake species and populations in the form of CITES provisions. Animal lovers in many countries now propagate 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 computer action games.
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.
Snakes for sale
You can find almost any kind of snake for sale. However you must be careful not to buy a snake that is poison producing or a snake that will grow too large to be handled.Remember, snakes are wild animals and if not controlled can be dangerous for children and pets.
Snake Cages
Each of these snake cage enclosures are hand crafted and designed specifically for your animal's needs. These enclosures are especially suited for housing reptiles because of the habitat they are capable of providing.Most of these enclosures can be personally delivered and set up by me including interior settings as a complete package.
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These Enclosures can also have the potential of providing an environment suitable for mixing various reptiles, small birds & fish to cohabit together. And best of all, the maintenance is quick because it comes equipped with an easy rinse & flush system.
