snake It is an elongated reptile that lacks legs that belongs to the suborder Serpentes. Its body is covered in overlapping scales. Their skull has greater joints than their ancestors the lizards that allow them to feed on prey much larger than themselves.

Species

There are more than 3.000 species of snakes distributed throughout the world. You can see a list of snakes ordered by their common name, in this link. (in English)

Features

The snake has different lengths depending on the species to which it belongs. The largest species is the reticulated python which is about 6,95m long and the green anaconda which is about 5,21m long, which is also considered the heaviest snake on earth weighing 97,5kg . At the extreme, of the smallest snakes, is the Leptotyphlops carlae with a length of about 10,4 cm. Most snakes are quite small averaging 1 m long.

Life expectancy varies according to the species and the habitat where it lives, but the average lifespan is about 20 years in the wild. In captivity, some species can live up to 50 years.

The skeleton of most species of snakes is made up of the skull, hyoid, spine and ribs, although henoid snakes retain vestiges of the pelvis and hind limbs. The skull consists of a solid and complete neurocranium, which is attached to small bones, in particular the bones of the jaw that are very mobile and that greatly facilitate the handling and ingestion of large prey. The left and right sides of the lower jaw are united only by a flexible ligament at the anterior tips, which allows them to be widely separated, while the posterior end of the lower jaw bones articulates with a quadratic bone, allowing greater mobility. The jaw and quadratic bones can pick up ground vibrations. Some snakes can even detect the position of prey, resting their jaw on a flat surface that gives them sensitive stereo hearing.

The vertebral column is made up of vertebrae that vary between 200 - 400. The tail vertebrae are comparatively few in number (less than 20% of the total) and do not have ribs, while the vertebrae of the body each have two ribs that are articulated. with them. The vertebrae have projections that allow a strong union of the muscles that allows locomotion without limbs.

Tail autonomy, a trait that some lizards possess, is absent in most snakes. Caudal autonomy is rare and intervertebral and not like that of lizards, which is intravertebral, that is, rupture occurs along a predefined fracture plane present in a vertebra.

In boas and pythons there are remnants of the hind limbs in the form of a pair of pelvic spurs. These small claw-like protrusions on either side of the cloaca are the outer part of the vestigial skeleton of the hind limb, which includes the remains of an ilium and a femur.

Snakes are polythodont, that is, their teeth are constantly being renewed.

The heart is encapsulated in a sac, called the pericardium, located at the bifurcation of the bronchi. However, the heart can move when a diaphragm is missing, an adjustment necessary to allow large prey to be swallowed without damage. The spleen attaches to the gallbladder and pancreas and filters the blood. The cardiovascular system is unique, due to the presence of a portal renal system in which blood from the tail passes through the kidneys before returning to the heart.

The left lung is poorly developed and is small or sometimes even absent, since the tubular bodies of snakes require that all their organs be long and thin. In most species, only one lung is functional. This lung has a vascularized anterior portion and a posterior portion that does not function in gas exchange. This "saccular lung" is used hydrostatically to regulate buoyancy in some aquatic snakes and its function remains unknown in terrestrial species.

Many of the organs that are paired, such as the kidneys or reproductive organs, are interspersed within the body. Snakes do not have lymph nodes.

Coiled snake

Coiled snake

Perceptions

Some snakes, such as snakes, pythons, and some boas, have infrared-sensitive receptors located in deep grooves of the snout, which allow them to perceive the heat radiated by warm-blooded prey. In vipers the grooves are found in the nostril and eye on each side of the head. Other snakes with infrared vision have multiple smaller labial holes that cover the entire upper lip, just below the nostrils.

The scent of prey is also used by snakes to locate them. They sniff their prey using their forked tongues to collect airborne particles, which pass to the vomeronasal organ where they are examined. The tongue of snakes has the sense of smell and taste at the same time. The tongue is constantly kept in motion to sample air, soil and water particles to determine the presence of prey or predators. The tongue also works the same way in water-dwelling snakes like the anaconda.

The vision of the snake varies greatly between species, some are only able to perceive light in the dark or have sharp vision. But the normal thing is that most species have adequate non-acute vision that allows them to follow movements. The best vision is found in arboreal snakes and is weakest in early riser snakes.

Certain species of snakes possess binocular vision, such as the asian vine snake (genus Ahaetulla), which are able to focus to the same point with both eyes. The vast majority focus by moving the lens back and forth relative to the retina, while other groups of amniote the lens is stretched. The nocturnal species have cut pupils and the diurnal pupils are rounded.

Leather

The skin of snakes is covered in scales. Their skin is popularly believed to be slimy when visually associated with worms, but their skin texture is smooth and dry. The scales are specialized to be able to travel or cling to surfaces. The body scales can be smooth, keelike, or granular. The eyelid of a snake is also a scale, but transparent "glasses" that remain permanently closed.

The scales have a great diversity of color patterns. These patterns are related to the behavior of the species and to certain functions. Snakes that are flat or have longitudinal stripes tend to escape their predators and the pattern or lack of it allows the snake to go unnoticed. Other snakes with more common patterns use active hunting strategies where the pattern allows them to send little information to their prey about their movements. The red snake often uses ambush-based strategies, because their pattern helps them blend in with the environment they are in.

Young

The detachment of the scales is called ecdysis, although popularly known as molt. It fulfills the function of replacing old and worn skin or getting rid of parasites such as mites and ticks. In insects, the replacement of the skin implies growth of the animal, but in the case of snakes it has been shown that this is not the case of snakes.

It occurs periodically throughout your life. Before molting, the snake stops feeding, and sometimes hides or moves to safety. Before shedding the skin, it becomes dull and dry, the eyes become cloudy or blue. The inner surface of the skin travels liquefies, allowing the old skin to separate from the new. After a few days, the eyes clear and the snake begins to shed its old skin. The old skin breaks near the mouth and in many cases peels back over the body from head to tail in one piece as if pulling a sock.

An adult snake can shed its skin once or twice a year, but young snakes that are in full growth can do so up to four times a year. The discarded skin gives the perfect impression of the scale pattern, making it possible to identify the snake if the skin is intact. In the scale count it is also possible to determine the sex of the snake if the species is not clearly dimorphic.

Poison

Poisonous snakes are classified into two taxonomic families:

  • Elapids - Some of the most famous are: Royal snake (Ophiophagus hannah), krait rayado (Bungarus fasciatus), black mamba (Dendroaspis polylepis), Copperhead pigmea (Austrelaps labialis), sea snakes and coral snakes.
  • Vipers - Some of the best known are: Rattlesnakes (Crotalus), copperhead snake (Agkistrodon contortrix)

There is a third family that contains the opisthtoglyphic (rear-tailed) snakes (as well as most other species of snakes):

  • Collusive - They include: Boomslang (Dispholidus typus), brown tree snake (Boiga irregularis), green vine snake (Ahaetulla nasuta). Not all species are poisonous.

Some species of snakes such as cobras or vipers use venom to immobilize or kill their prey. Venom is modified saliva that is delivered to the victim through the fangs. Many species, like the viper, have gaps between the fangs to inject venom more efficiently, while other snakes simply have a groove on the rear edge to channel venom into the wound.

Birds, mammals, and other snakes (such as king snakes) that feed on poisonous snakes have developed immunity to certain poisons so that they can be consumed without harm.

The common term "poisonous snakes" is a mislabel for snakes. A venom is inhaled or ingested, while snakes inject the venom through their fangs. However, there are always exceptions. The snakes of the genus Rhabdophis obtain the poison from the toxins of the toads on which they feed and then expel it through the nuchal glands to protect themselves from their predators. A species of American snake that lives in the state of Oregon produces the poison through the newts that it feeds on and stores them in their livers to be poisonous to predators.

Venom is made up of proteins and is stored in poisonous glands in the back of the head. In all venomous snakes, the glands communicate through hollow ducts in the upper jaw (tusk). Proteins are a mixture of neurotoxins (which attack the nervous system), hemotoxins (which attack the circulatory system), cytotoxins, bungarotoxins or other different ways of attacking the victim. The venom contains the enzyme hyaluronidase, which is responsible for spreading the poisons rapidly throughout the body.

Species that use hemotoxins have fangs in the front of the mouth that facilitate injection, while those that use neurotoxins have fangs in the back of the mouth, rolled back. This makes the injection as well as the extraction of the poison difficult. Elampids, such as cobras or kraits, have hollow fangs that cannot be raised to the front of their mouths, and cannot "stab" the victim like a viper does. To harm it they must bite.

Locomotion

Side ripples

Although snakes do not have limbs, they are capable of moving by lateral undulations. It is the only mode of locomotion by water and the most common of locomotion by land. In this mode the snake's body moves left and right, producing a series of "waves" that move backward. The waves push the snake against contact points found in the environment, such as rocks, branches, irregularities in the ground, etc. Each of these objects generates a reaction force directed forward and toward the snake's midline.

The speed of this movement depends on the density of the push points in the environment. The speed of the wave is the same speed of the snake, as a result, each point on the body of the snake follows the path of the point that precedes it. This allows the snake to move through very dense vegetation and small openings.

Side winding

When a snake must move in areas that have no irregularities to push against, such as a slippery mud or sand dune, side winding is used. It is a modified form of lateral undulation in which all segments of the body oriented in a single direction remain in contact with the ground, while other segments rise, which results in a rocking motion. This mode has an extremely low caloric cost. There is a belief that this movement is due to the fact that the sand is hot, but there is no scientific evidence to corroborate it.

Concertina locomotion

When there are no push points and there is not enough space for lateral winding, snakes must resort to concertina locomotion. This type of locomotion is used in tunnels. In this mode, the snake must hold the back of the body against the wall of the tunnel, while the side straightens and extends. The front part flexes to form an anchor point, and the back part straightens and pulls forward. This mode is very slow and demanding, with a caloric cost seven times higher than undulating locomotion at the same distance traveled. This high cost is due to the frequent stops and starts of parts of the body, as well as the great need to use active muscular effort to support the walls of the tunnel.

Arboreal locomotion

Tree snakes use various modes of locomotion depending on the species and texture of the tree's bark. They generally use a modified form of concertina locomotion on smooth-textured branches, but undulate laterally if contact points are available. They move faster on small branches when the contact points are present, unlike animals with limbs that move better when the branches are thicker.

Rectilinear locomotion

Rectilinear locomotion is the slowest mode. It is the only way that the snake does not need to bend its body laterally, although it can turn it. In this mode, the belly scales are raised and pulled forward before being placed down and the body pulls on them. The waves of motion and stasis pass posteriorly, resulting in a series of ripples in the skin. The ribs in this mode do not move. This method is used by various snakes to sneak up on prey in open terrain.

Behavior

Snakes are ectothermic animals, that is, they must regulate their own body temperature. They should warm up in the sun and move to colder places to cool off. During winter, in regions where it is very cold, snakes cannot stay active and go into vegetative rest. Unlike hibernation where mammals are completely asleep, reptiles are awake but remain totally inactive. They hide in burrows, under rocks or in tree holes.

Habitat

The snake can be found in various habitats, both terrestrial and aquatic including water, forests, deserts, and grasslands. The most abundant and largest inhabit tropical forests.

Although they need heat to live, there are species in cold areas, such as those that live near thermal areas where they find the necessary heat. However, there is a species capable of surviving very cold environments, such as the european common viper (Vipera brush) Which is the only species that inhabits the Arctic polar cycle.

Several species can live in the mountains. Snakes have been found at a height of 4877 meters. They live on the ground or create underground tunnels where they easily find food and shelter.

They do not inhabit snakes near large cities or urban areas because they feel very stressed by the large vibrations emitted by large populations of humans.

Distribution

The snake is distributed from the Arctic Circle in Scandinavia to Australia. They can be found on any continent except Antarctica where it is too cold to survive and in areas such as the sea or 4.900 m in the Himalayan mountains. There are also some islands where snakes do not have a presence, such as Ireland, Iceland, Hawaii and New Zealand.

Food

Snakes are strictly carnivorous animals. They feed on small animals such as lizards, frogs, other snakes, mammals, birds, eggs, fish, snails, or insects. To feed they must swallow their prey completely, since they lack the ability to tear their prey to pieces. The size of the snake determines the size of the prey, since when swallowed whole it must have a size similar to the snake that consumes it. For example, young pythons go from feeding on small rats or lizards to feeding on small deer or antelope as adults.

There is a popular belief that snakes are capable of dislocating their jaws, but they are not. It simply has a highly flexible lower jaw with the ability to swallow prey even if it is larger than the diameter of the snake. For example, the African egg-eating snake has a jaw so flexible that it is capable of eating eggs much larger than the diameter of its head. This snake does not have teeth, but it can break the shells of eggs with a bony protrusion that it has on the inside edge of its spine.

Some species specialize in killing other snakes, such as king cobras and the Australian bandy-bandy. Snakes in the Pareidae family have more teeth on the right side, as their prey's shells often spiral clockwise. Those that possess poison kill their prey and wait for it to die to eat them. Others kill it by constriction and still others swallow it whole and alive.

Once they have fed, digestion begins. During this process the snake remains inactive, since they consume a lot of energy, especially if they have been feeding on large weights. In sporadic feeding species, the intestine enters a reduced state between meals to conserve as much energy as possible. The digestive system must be regulated, which means that the snake cannot feed for 48 hours. Temperature plays a very important role in digestion, as they are cold-blooded animals. The ideal temperature to digest is 30 ºC. They must use so much metabolic energy that the temperature of the rattlesnake (Crotalus durissus) rises about 1.2 ° C. If a snake feels threatened or is disturbed it will expel the prey in order to escape. If none of this happens, the digestion process will effectively end with the enzymes dissolving and absorbing the nutrients minus the hair (or feathers), claws or excrement that are expelled.

Green tree python (Morelia viridis)

Green tree python (Morelia viridis)

Predators

The snake has many types of natural predators. They vary depending on where they live and the size of the species. The youngest are more likely to be attacked, than the older ones that are avoided. The young can be attacked during their stage as embryos (eggs) or quickly after hatching.

Birds are the most common threat, as they can spot them from the sky and plummet in an instant. They can find snakes on land, sea, and even in trees.

Large snakes are preferred by wild boars. They are very aggressive animals capable of facing the challenge. To achieve this they hunt in a group if the snake is very large. They are able to identify which are poisonous and which are not.

Raccoons, foxes, and coyotes also consume many species of snakes, but they tend to shy away from poisonous ones. Being fast you can also reach the snakes that inhabit the trees.

King snakes feed on other snakes. They actively seek them out. Other snakes can become cannibals when they cannot find another type of food.

Humans are also part of the predators of snakes, sometimes they are accidental deaths when they are run over in the cart but others are on purpose, either because they do not like them or because they are afraid of being bitten. They are also consumed as food in some regions of the world.

Reproduction

Each species uses a different method of courtship. Ritual combat between males to obtain the females they want to mate with includes tactics such as topping, a behavior exhibited by most vipers where the male twists around the elevated body of his opponent and forces him down. Neck bites while intertwined are common among all species.

Among all snake species there are different modes of reproduction, although all use internal fertilization. This is achieved by paired and forked hemipenis on the male's tail. The hemipenis are ribbed, hooked or twisted in order to reach the cloaca of the female.

Most species lay eggs, and later, they are abandoned. However, some species (such as the king cobra) build the nest and stay nearby after incubation. The snakes wrap themselves around their eggs, "shivering" to generate heat and remain with them until they hatch. Female pythons never leave their eggs except to bask in the sun or drink water.

Some species are ovoviviparous animals and keep their eggs inside their bodies until they are ready to hatch. Other species are strictly viviparous, such as the boa constrictor and the green anaconda, which feed their young through a placenta and a yolk sac. This is very unusual among reptiles. Retention of eggs and live births are more common in cold environments, as it is more effective to maintain temperature internally than externally.

Optional parthenogenesis

Parthenogenesis is another form of reproduction that some snakes possess in which the growth and development of the embryos occurs without fertilization. The copperhead snake (Agkistrodon contortrix) Y Oriental cottonmouth (Agkistrodon piscivorus) can reproduce by this method, that is, they are capable of reproducing by both methods, both asexually and sexually. The process involves self-fertilization of the eggs or the division of cells. To have more information on the process we recommend the following link.

Species that possess scales reproduce sexually, with the exception of the good colombian rainbow (Epicrates maurus) that can reproduce by facultative parthenogenesis

State of conservation

Snakes are classified as an endangered species and are protected by the Endangered Species Act. Its main threat is death on the roads and the destruction of habitat, due to deforestation.

Relationship with humans

Bite

Snakes do not usually bother humans unless they bother them, as most prefer to avoid them. Most snakes are not dangerous to humans, with the exception of constrictors and poisonous ones. The bite of a non-venomous snake is harmless to humans, as they do not have teeth adapted to tear, although there is the possibility of suffering an infection or tissue damage. The World Health Organization (WHO) classifies snakebites in the category of "other neglected diseases."

Deaths from bites are very rare. Non-fatal venomous snake bites often result in amputation of the affected limb. Of the 725 venous species, only 250 are capable of killing a human with a single bite. The areas most affected by bites are: Australia with only one fatal bite a year, India with some 250.000 bites a year and 50.000 registered deaths. The WHO estimates that 100.000 people die each year from a snake bite.

Treatment for a bite varies as much as the bite itself. The most common and effective treatment is the antidote, a serum made from snake venom. There are specific antidotes for each species (monovalent), while others are intended for multiple species (polyvalent). To produce the antidote for pit vipers, the poisons of different species of rattlesnakes, copperheads and cottonmouths are mixed in the body of a horse, in smaller and larger doses until the horse becomes immune. Blood is drawn and separated, purified, and lyophilized. It is then reconstituted with sterile water and becomes an antidote. For this reason, people who are allergic to horses are more likely to have an allergic reaction to antidotes. In the rest of the world, such as India, South Africa, and Australia, antidotes are made in a similar way.

Snake charmers

In some areas of the world, especially in India, there are snake charmers. It is a show where the charmer carries the snake in a basket that he seems to embody playing melodies from his wavy musical instrument, to which the snake responds. Snakes do not have external ears, although they do have internal ears, but they do not respond to sound, but to the movement of the flute.

The Wildlife Protection Act of 1972 in India technically prohibits the charm of snakes in order to reduce cruelty to animals.

Trampa

The Irula tribes of Andhra Pradesh and Tamil Nadu in India have been hunter-gatherers in the hot, dry forests of the plains, practicing the art of catching snakes for generations. Their vast knowledge of snakes allows them to capture them with the help of a simple stick. The snakes were captured for sale for skins, but after prohibition under the Wildlife Protection Act of 1972, the Irula Snake Collection Cooperative was formed to obtain the venom and make antidotes. The snakes are released into the wild, after being captured after four extractions.

Food

In some cultures snakes are suitable as food. It is even considered a highly prized delicacy for its supposed pharmaceutical effect of warming the heart. The snake soup is consumed in the autumn in Cantonese cuisine to warm the body. In western cultures they are consumed in circumstances of dire need. The exception is rattlesnake meat that is cooked in parts of the Midwestern United States.

In countries such as China, Taiwan, Thailand, Indonesia, Vietnam, and Cambodia, drinking snake blood, particularly cobra blood, is thought to increase sexual virility. The blood is drained while the cobra is alive and is often mixed with a liquor to enhance the flavor.

In Asian countries the use of snakes with alcohol is also accepted. In this case, the body of the snake is immersed in liquor. This is said to make the liquor increase in price and be stronger. For example, the Habu snake is used to create Okinawan Awamori liquor, popularly known as "Habu Sake."

Snake wine (蛇 酒) is an alcoholic beverage produced by infusing whole snakes in rice wine or grain alcohol. It was created in China during the Zhou dynasty.

Pets

In the West, some snakes like the royal python (Python regius) And corn snake (Pantherophis guttatus) are kept as pets. To meet the demand a captive breeding industry has been developed, which are preferable to wild captured individuals. They are easy to maintain pets, requiring minimal space since most species are only 1,5 m tall. You can also feed infrequently, once every 5 to 14 days. If properly cared for, certain species can last more than 40 years.

Medicine

Various compounds in snake venom are being investigated as possible treatments for pain, cancer, arthritis, stroke, heart disease, hemophilia, and hypertension, and to control bleeding (for example, during surgery).

Popular culture

Many cultures have adapted the snake as a sacred being throughout history. In Egypt, the serpent plays a leading role with the Nile cobra adorning the pharaoh's crown in ancient times. He was revered as one of the gods and was also used for sinister purposes: the murder of an adversary and ritual suicide (Cleopatra). The ouroboros was a well-known ancient Egyptian symbol of a serpent swallowing its own tail.

In the Bible, King Nahas of Ammon, whose name means "Serpent," is described very negatively, as a particularly cruel and despicable enemy of the ancient Hebrews. Imperial Japan depicted as an evil snake on a World War II propaganda poster. India is often called the land of snakes and is steeped in tradition regarding snakes. They are still being worshiped today.

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