SNAKES

Ball python
Snakes are scaled reptiles classified in the Order Squamata, which also includes their close relatives the lizards. There are over 3,000 species of snake, ranging in size from pencil-size African thread snakes to 25-foot anacondas large enough to swallow a human child. They live in almost every ecological niche, except the polar regions, and are particularly plentiful in tropical regions and deserts. [Source: Adrian Forsyth, Smithsonian, February 1988; Frederick Golden, Time magazine, October 13, 1997; Kevin Short, Daily Yomiuri, June 21, 2012]
Snakes are vertebrates. Among reptiles, snakes are most closely related to monitor lizards and Gila monsters. All these creatures have forked tongues and sense organs on the roofs of their mouth.
Colubrids, sometimes referred to as typical snakes, are the largest snake family, accounting for almost two thirds of all species. Common features among colubrids include a lack of a left lung, and backlimb girdel. Garter snakes, grass snakes, whip snakes and all rear-fanged venomous snakes are Colubrids. Colubrids are regarded as more developed than primitive blind snakes, thread snakes, and boas and pythons. Most dangerous venomous snakes are not Colubrids. They are front-fanged snakes.
Some snakes are easily killed by prolonged shelter to the sun that is why they often seek shade in the middle of the day. In temperate climates many snakes hibernate for three or four months in the winter: they don’t eat that entire time yet emerge at about the same weight as when they started. In some places some species gather in large numbers and live in the same den, which they return to year after year.
See Separate Articles: VENOMOUS SNAKES: THEIR VENOM, BITES AND ANTIVENINS factsanddetails.com ; VENOMOUS SNAKES AND HUMANS: BITES, ANTIVENINS, WHAT TO DO factsanddetails.com REPTILES factsanddetails.com
Websites and Resources on Snakes: Snake World snakesworld.info ; National Geographic snake pictures National Geographic ; Snake Species List snaketracks.com ; Herpetology Database artedi.nrm.se/nrmherps ; Big Snakes reptileknowledge.com ; Snake Taxonomy at Life is Short but Snakes are Long snakesarelong.blogspot.com; Websites and Resources on Animals: Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org
Snake History

russell's viper
Herpetologists believe snakes developed from a group of lizardlike creatures that took up a burrowing lifestyle. Living in loose soil or leaf litter, these animals gave up their legs for a slithering style of locomotion, using the movable scales on their stomach as anchors for pulling themselves along the substrate. [Source: Kevin Short, Daily Yomiuri, June 21, 2012]
Snakes most likely evolved about 90 million years ago from lizards that took to living underground or in forest litter and lost the use of their legs. Evidence of this includes the snake's lack of an eardrum (underground animals generally have no use for hearing) and the remnant of leg and pelvic bones still found in many snakes. Pythons, for example, have tiny leg bones which may be visible as minuscule claws at the base of their tails.
But the matter of how snakes evolved is far from settled. For some time there has been a debate on whether the first snakes evolved on land or in the sea. Some think they evolved from monsaurs, an extinct group of large marine reptiles. Even if this case it clear from anatomical evidence that modern aquatic snakes descended from terrestrial snakes.
In April 2006, scientists, announced the discovery of the oldest known snake in Patagonia. Measuring less than a meter in length and given the name Najash rionegrina, the fossil back up the case that snakes evolved on land. The skeleton contains a bone structure that support the pelvis, a feature lost by sea creature long before, two small rear legs and anatomical features suggesting that it lived in burrows. The deposits in which it was found also indicate it came from a terrestrial environment. The creature likely moved around like a snake. The purpose of the two legs is unknown.
In February 2009, Jonathan Block, a vertebrate paleontologist at the University of Florida, announced the discovery of a fossil of the most enormous snake ever found: a giant boalike snake that lived 60 million years ago that was as long as a bus and large enough to eat crocodiles and 150-kilogram giant turtles. Based on the size of it vertebrae the creature weighed between 730 kilograms and two tons and measures between 11 and 15 meters and was more than 1.25 meters wide at is widest point. The fossil was found in one of the world’s largest open cast coal mine in Cerrejon, Columbia. It was named Titanoboa, more or less meaning gigantic snake (See Below). Block told AFP, “Truly enormous snakes really spark people’s imagination but reality has exceeded the fantasies of Hollywood. The snake that tried to eat Jennifer Lopez in the movie “Anaconda” is not as big as the one we found.
Biggest, Longest and Smallest Snakes

snake scales
According to Britannica, the smallest identified snake in the world is the Barbados thread snake, which reaches a length of 10.4 centimeters (4.1 inches). The reticulated python of Southeast Asia is the longest snake in the world, according to the Natural History Museum. On average, it reaches 6.25 meters, (20.5 feet). [Source: Olivia Munson, USA TODAY, March 13, 2023]
The longest recorded reticulated python was discovered in 1912 and measured 10 meters (32.8 feet) — longer than the height of a giraffe. The largest and heaviest reticulated python kept in captivity was Medusa, who reached 7.67 meters (25 feet) and weighed 158.8 kilograms (350 pounds). On average, reticulated pythons weigh around 158 kilograms (350 pounds).
The heaviest — and therefore biggest snake in the world is green anaconda, a semiaquatic snake that lives in South America and Trinidad, particularly in or near swamps, marshes, slow streams and rivers. National Geographic say they can weigh up to 250 kilograms (550 pounds). According to the the Natural History Museum, the heaviest anaconda on record weighed 227 kilograms (500 pounds). Generally, green anacondas reach lengths of six to nine meters (20 to 30 feet), according to National Geographic.
The biggest snake ever was the Titanoboa, which lived during the Paleocene Epoch (66 million to 56 million years ago) and is considered "the largest known member of the suborder Serpentes," according to Britannica. Adult Titanoboa are estimated to have been 13 meters, (42.7 feet) in length and weighed approximately 1,135 kilograms (1.25 tons). The Titanoboa was the largest predator on Earth following the extinction of the dinosaurs 65 million years ago and until the first appearance of the Megalodon around 23 million years ago, according to the Florida Museum of Natural History.
Snake Characteristics
A snake's internal organ have been shrunken, stacked on top of one another and ingeniously engineered to fit in their body. Their skeleton consists of flexible backbones and dozens of pairs of ribs. Their skins is covered by scales and is generally dry to the touch.

Most snakes have only one lung. It is exceptionally long, reaching well into the snake’s body. When the lung is full of air it looks almost as if the snake has swallowed another snake. Snakes lack a diaphragm muscle to push their lungs. Their rib muscles which expand the chest during each breath also propel the body forward when the snake moves.
Snake scales don't grow so the skin has to be shed when the snake gets bigger. Snakes shed their skin several times a year. Before this occurs their skin color is dull and their eyes are milk colored. Snakes are partially blind at this time and usually try to stay hidden. A couple of days before the shedding begins, the color returns to the skin and eyes. An oily secretion collects under the old skin and loosens it, and the skin cracks at the lips. The snake rolls back the skin, often with the help of a rock, and begins crawling out, rolling the skin inside out like a glove as it moves out. The eyes covers are shed along with the skin.
The skins from cobras, pythons, lizards, water snakes and other snakes has a beautiful texture and patterns. They are used to make expensive shoes, handbags, luggage, belts and garments. The bright colors found on some poisonous snakes is a warning to potential predators that the snake is dangerous to them. Some non-poisonous snakes have patterns that mimic poisonous snakes , which are intended to scare off predators. Occasionally you get bright blue rattlesnakes due to a genetic defect.
Some snakes dig burrows. Most of those that do — along with other legless creatures that dig burrows — usually rely on their heads to excavate or compact earth. The eastern hognose snake has a protuberance on its head that helps it scrape away the soil and compact it upwards, The Louisiana pine snake loosens sand and soil with its “nose” and “hoes” it out by bending its head downward. The shield nose cobra move sits head from side to side, scraping the soil and with its flat shield, the Saharan pit viper buries itself by flexing its side and twisting to scoop out sand. [Source: Natural History, December 2006]
The only vocal sounds that most snakes make are hisses. Some growl. Snakes of all species shake their tails when agitated, but only rattlesnakes can make a noise with their tails. Some species of snake play dead when they sense danger.
Lizard and Snake Senses
Lizards have movable eyelids (snakes don't have these) and most species have excellent eyesight. Some species of lizard even have a "third eye." on top of their head. This eye does not form an image but may help a lizard distinguish between light and dark. Lizards also have external eardrums and can hear very well.
Lizards and snakes are both very good at sensing and analyzing smells and message-carrying chemicals Many have a vomeronasal organ embedded in the roof of the mouth that detects heavy non-airborne molecules taken in through the mouth. It supplements olfaction which is the ability to smell airborne molecules that enter the nostrils and is distinct from taste, which analyzes chemicals that come into contact with taste buds on the tongue. These senses help reptiles locate prey and help warn them or potential prey that might be toxic. It also frees up the eyes to locate prey and find mates.
The vomeronasal organ is sometimes called the Jacobsen's organs. Lizards and snakes with forked tongues have these on either side of the roof of their mouth. Chemicals are picked up from the environment with their forked tongues then transfer to these organs.
Lizards and snakes with forked tongues constantly flick their tongues in and out of their mouths, bringing in new samples of chemicals on either side of the tongue through the chemical equivalent of stereoscopic vision. Not only can they determine the presence of chemicals they can also determine the direction which they are coming from and detect edges and dimensions of the sources. .
Snakes use forked tongue and sense organs in their mouth to locate food, enemies and mates . And this they can do without even opening their mouths. Predators rely on smells and message-carrying chemicals to locate their prey and use eyes to determine the location of the prey for the final lung.
Snake Senses

Snakes have keen senses of smell, temperature and touch but generally have poor eyesight (except night snakes that have catlike eyes). Snakes don't have movable eyelids, and consequently they can not blink. Their eyes are covered and protected by transparent scale called a brille. Kevin Short wrote in the Daily Yomiuri: In their process of adapting to an underground lifestyle, snakes gave up their external ears and eyelids. Like most reptiles, snake vision is designed for picking up movement of potential prey, rather than separating stationary objects. Their finest sense, however, rests in their very well-developed Jacobson's organs. These organs, which sense pheromones and other invisible chemical messengers, come in pairs, and are located to the right and left inside the mouth. The forked tongue so characteristic of snakes is actually designed to collect pheromone samples from the air and ground. When retracted the respective tongue tips are placed against the right and left Jacobson's organs, allowing the snake to compare the results and compute from which direction the pheromones are coming.
Like most reptiles, snake vision is designed for picking up movement of potential prey, rather than separating stationary objects. Their finest sense, however, rests in their very well-developed Jacobson's organs. These organs, which sense pheromones and other invisible chemical messengers, come in pairs, and are located to the right and left inside the mouth. The forked tongue so characteristic of snakes is actually designed to collect pheromone samples from the air and ground. When retracted the respective tongue tips are placed against the right and left Jacobson's organs, allowing the snake to compare the results and compute from which direction the pheromones are coming.
Unlike lizards, snakes don't hear very well. Although most snakes are deaf or nearly deaf, they do have internal ear-bones that enable them to hear some very low frequency sounds, but function mainly to detect minute ground vibrations. Snakes lack eardrums external ears, which are believed to have been lost from when they first evolved underground from burrowing reptiles millions of years ago. They have retained some of their ear bones and can sense vibrations through their jaws.
Rattlesnakes, pit vipers and other snakes have heat-sensitive, infra-red-detecting facial pits that allow them to detect prey several meters away. Information from the pits and eyes is processed in same area of the brain, allowing the snakes to “see the body heat of an animal perhaps as a brighter image.” Some animals have built in defenses against a rattlesnakes heat sensing capabilities. Ground squirrels keep their tail cool when they sense most kinds of snakes. But if a rattlesnake comes near they heat up their tails and furiously move them from side to side — a process called tail wagging — to thwart an attack.
Snake Movement

snake pit organs
The skeleton of a snake is essentially a skull connected to a long spinal columns and rib cage. Most of the muscles run longitudinally between the vertebrae and the ribs. Some are short connecting one rib to another. Other are longer, spanning as many as 40 vertebrae. When muscles are contracted they move close together, causing a section of snake to curve.
Snakes move forward by making their skin crawl. Most snakes have horny, backward-pointing plates on the undersides of their bodies that overlap and grip the ground. Muscular movements within the body move the snake forward.
Snakes move by producing alternating waves of muscles contractions. Describing this movement, David Attenborough wrote: "They flex their flank muscles in alternate bands so that their body is drawn into a series of S-shaped curves. As the contractions ravel in waves down their body, their flanks are pressed against obstacles on the ground such as stones or plant stems and the snake is able to push itself forward. In short it wriggles. If it is put on a surface completely free of any irregularities...the technique fails and the snake simply writhes helplessly."
When hunting, it is very important for snakes to move quietly and with a minimum of movement so as not to alert its prey. Under these circumstances, the snake approaches the prey straight on, keeping its is head still, body straight and slowly moving forward by using contracting muscles on its belly.
A striking snake arches its body near its head to for form an "S" and then straightens out its body. A completely snake can not strike. A striking snake an generally only strike out half a body length
Many snakes are good climbers, using the scales on their undersides to grip on to on bark, or winding themselves around branches. In the rain forest you are more likely to find snake sin the trees than on the ground. Many snakes are also good swimmers They can inflate their lung to float on the top of the water an use their belly scales to grip the surface of the water and slide across the water almost as easily as they do on land.
Snake Breeding

baby King cobra
Male snakes have two sex organs (called hemipenises) hidden behind a flap at the base of their tails. Some species use them alternatively in quick, successive couplings or gang-bang orgies. Others favor one hemipenis in long copulation that deters rivals.
The Brahminy blind snake is a snake species with no males. Females lay their eggs without having them fertilized by a mate. The snakes habit of hiding away in potted plants has enabled to spread all over the world.
Female snakes sometimes store sperm inside their bodies for several months until a climate change signals the snake it is the right time to start fertilization. Pregnant females are sometimes unable to feed during the later part of their pregnancy and go months without feeding, relying on fat stored in their bodies.
Most snakes lay eggs but some give birth to live young that hatched from eggs inside the female snake's body. Snake eggs usually have a soft, flexible, non-brittle shell. The young are born encased in a membrane that breaks. Some species lay their eggs among rotting leaves or logs to keep them warm. The eggs can take several days to several months to hatch. The determining factor as to when they hatch is hot the weather is.
Depending in the species, snakes lay between 2 and 100 eggs with most species laying between seven and nine. Young snakes have a special scale at the end of their end of their nose call the egg tooth which they use to break out of their leathery shells.
Snake Hunting and Feeding Behavior
All snakes are carnivorous and they prefer live prey. They often rely on stealth to capture prey and swallow it whole. Small species eat insects, worms, slugs, scorpions and frog's eggs. Medium size ones eat mice, baby birds, eggs, frogs, fish and other small animals. Large snakes can eat small mammals, other snakes, birds, and even babies. Some species can consume prey that is two and half times their body weight.
Snakes rarely eat more than once a week, unless their prey is really small. On average a snake takes 12 to 14 days to digest a meal, and it is not unusual for a snake to go several months without eating After a big meal some snakes remain inactive for several days while it digests its prey. If a snake is threatened it sometimes regurgitates its meal so it can escape more quickly.

cobra
Many snakes like to laze around and hang out in places their prey is most likely to pass, stalk their prey when it gets near and get close enough to strike. Many snakes have camouflage markings and an ability to stay very still so they are not detected. Many can catch their prey with a single strike. Some species specialize in going into the holes of burrowing animals. Many climbing snakes seek out nests and feed on eggs and chicks. A few species use their tails as lure prey which mistake the tail for a worm or caterpillar
Snakes that feed on large, potentially-dangerous creatures kill them first, usually by poisoning or through constriction. Large prey is swallowed head first. Otherwise the legs might get caught up in the snake’s throat. The insides of the snake clamp down on the prey, preventing it from moving or opening its mouth to damage the inside of the snake.
Everything but hair and feathers is digested. Some snakes that primarily eat eggs swallow the eggs whole and a sharp objects in their gullets break the shell, which is when spit out. Many snakes can go months or years without drinking, instead getting the water they need from their food. Those that do drink stick their heads under water and use their jaws to pump water into their body or suck water from wet leaves.
Snake Feeding Anatomy
Snakes are unable to dismember their prey and must swallow it whole. They have a lower jaw bone that is divided in half and hinged with ligament that stretches sideways. The bones supporting the lower jaw on the skull are movable so the mouth can open very wide. These things allow snakes to swallow food that is larger than themselves.
Snakes are able to breath and not choke when they swallow large prey because their windpipe extends almost to the end of their mouth and they have special muscles that pull the windpipe opening forward past the prey as it is being swallowed.

python skull
The fangs and teeth of most snakes point backwards which helps force large prey towards the throat and keep even slippery creatures such as frogs from slipping back out. Snakes move prey into their gullet by alternately moving the right and left sides of their jaws, Depending on the size of the prey the process can take from a few seconds to a few hours but generally takes a few minutes.
Rippling muscles inside the snake move the prey towards the stomach. Sometimes the prey remains alive while it moves through the snake’s throat. The prey of poisonous snakes often dissolved from the inside out inside the snake.
In order to swallow many snakes crawl over their food by contracting their muscles, pushing their bodies on the ground and their prey inside their bodies at the same time. Some snakes rotate their jaw forward, then pull it backwards, and "walk" their head over the victims. Snail eating snakes rotate their jaws in such a way that they hook the snake and pull it from the shell.
Constricting Snakes
Snakes like boa constrictors and pythons seize their prey with their mouths, and wrap their coils around it so the prey can no longer expand its chest and breath. It was often thought that these snakes kill through suffocation, crushing or choking. But often something more than mere suffocation is also going on. A suffocated rat, for example, usually dies in four minutes. A rat killed by a constricting snake dies in one minute. Studies indicate that snakes disrupt the circulation of their victims, doubling their victims’ blood pressure so that heart can not pump sufficient blood to the brain, lungs and other tissues, killing with a heart attack or stroke.
Constriction is the term used to describe the suffocation methods of suffocating snakes. Although some species of venomous and mildly venomous snakes use constriction to subdue their prey, snakes that employ the technique venom. In many cases the suffocating snake strikes at its prey and holds on, pulling the prey into its coils. In the case of very large prey, the attacking snake pulls itself onto the prey and wraps one or two loops around the prey, forming a constriction coil. The snake monitors the prey's heartbeat to ascertain it is dead. [Source: Wikipedia]
Contrary to myth, suffocating snake do not generally crush their prey, or break their bones. However, wild anacondas have been observed to cause broken bones in large prey. Also contrary to common belief, the snake does not suffocate the victim. A study of boa constrictors showed that constriction halts blood flow and prevents oxygen from reaching vital organs such as the heart and brain, leading to unconsciousness within seconds and cardiac arrest shortly thereafter In addition, many species of snakes have been shown to constrict with pressures higher than those needed to induce cardiac arrest.
Based in part on observations of oral and nasal hemorrhaging in prey, constriction pressures are also thought to interfere with neural processing by forcing blood towards the brain. This means that constriction can work by different mechanisms at varying pressures. It likely interferes with breathing at low pressures, can interrupt blood flow and overwhelm the prey's usual blood pressure and circulation at moderate pressures, and can interfere with neural processing and damage tissues at high pressures. During constriction when the prey's heart is impeded, arterial pressure drops while venous pressure increases, and blood vessels begin to close. The heart is not strong enough to pump against the pressure and blood flow stops. Internal organs with high metabolic rates, including the brain, liver, and heart, begin to stop functioning and die due to ischemia, a loss of oxygen and glucose.
Strikers and Lungers
Using high-speed video, Cornell herpetologist Bill Ryerson filmed snakes attacking dead rodents and found species fit into two broad categories: strikers and lungers — with the difference based on the kinds of teeth they possess. Sascha Pare, wrote in Live Science: Strikers attack at lightning speed from above, impaling their prey with needlelike teeth at the front of their lower jaw before wrapping their head over and around to inject venom with their fangs, or to squeeze the animal to death. These snakes include many boas, such as boa constrictors (Boa constrictor), and pythons.[Source: Sascha Pare, Live Science, January 17, 2024]
Kingsnakes, pine snakes (Pituophis melanoleucus) and some ground boas are lungers, according to Ryerson, who is a senior lecturer in anatomy at Cornell University's College of Veterinary Medicine. Lungers "strike more slowly and don't open their mouths as wide," Ryerson, who presented his research at the annual meeting of the Society for Integrative and Comparative Biology in January 2024, told Live Science. "They make contact with both jaws simultaneously."
Herpetologists have long focused their attention on snakes' fangs, which are teeth modified to inject venom, but they have largely ignored the rest of the teeth. "We just assumed they are all the same and will not tell us much about the evolution of snakes," Ryerson said. But Ryerson's work suggests otherwise. While a snake's other teeth may not catch our eyes quite the same as its fangs do, they are still important in how snakes evolved to attack and kill, he said.
"I've done quite a bit of work in the last few years on the striking behavior of snakes and I began to wonder how those teeth function in the ultrafast striking, especially for the non-venomous snakes like our boas and pythons," Ryerson said. While peering into the mouths of dozens of preserved specimens, Ryerson found that some snakes, such as boa constrictors, have narrow, upright teeth in their front lower jaw, while others, including kingsnakes, have stouter, curved teeth.
Then, Ryerson used X-rays to scan the jaws and teeth of almost 70 snakes from 13 species, Science reported. Using high-speed video, he also filmed snakes charging at dead rodents that he wiggled in front of them to analyze the snakes' striking behavior. His observations neatly sorted into two categories, Ryerson said. Strikers showed more variation in the size and shape of their teeth, which became shorter, broader and more curved toward the throat. Lungers, on the other hand, had broad, curved teeth all along their upper and lower jaws.
The fact that snakes have different dentitions wasn't so surprising, as it was "unlikely that all the teeth would be the same across all species," Ryerson said. "However, I was surprised by how well the shape of the teeth corresponded to the strike behavior."More specialized snake species, such as those that live in trees or underground, may not fit into either category, Ryerson said.
Image Sources: Wikimedia Commons
Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, CNN, BBC, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.
Last updated February 2025