Snakes are elongated, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. They are believed to have evolved from lizards (burrowing or aquatic), sometime around the Jurassic period. Currently, there are more than 20 recognized families of snakes, which include around 500 genera and 3,400 species. With so many different species, there are snakes of many different sizes. The world’s smallest snake, is know to be the thread snake, which grows to only about 3.9 inches (10 centimeters) long. It looks much like an earthworm. On the other side, the largest snake, the reticulated python, can grow to a whopping 30 feet (9 meters). The largest snake fossil ever discovered is called the Titanoboa. This creature lived 60 million years ago and would have been 50 feet (15 meters) long. Snakes live in almost every corner of the world. They are found in forests, deserts, swamps and grasslands. Many call underground burrows or the spaces under rocks home. Some snakes, like the cottonmouth water moccasin of North America live in water part of the time.
In parts of the West, snakes may be kept as pets. This is especially true of docile species, such as the ball python (Python regius) or the corn snake (Pantherophis guttatus). Apart from the attraction of an ‘exotic’ animal, this may also in part be because they are low-maintenance pets, requiring little space and less strict feeding schedules (every 5 to 14 days).
Though they are found all over the world, snakes do not, however, like the cold. This is because they are cold blooded or ectothermic. This means that they don’t have the means to regulate their body temperature like warm blooded creatures. If it is cold outside, then the snake will be cold, too, since their bodies do not use energy to create heat to warm them. When it is cold, many snakes hibernate in tunnels underground. Others seek warmer areas, such as inside humans’ homes.
Description and distribution of snakes
Their long, legless bodies are covered in overlapping scales and internally, skeletons are made out of a skull, a hyoid, a vertebral column, and ribs. Many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads with their highly mobile jaws. To accommodate their narrow bodies, snakes’ paired organs (such as kidneys) appear one in front of the other instead of side by side, and most have only one functional lung.
Their body shape depends on the habitat in which they live. Aquatic snakes usually have a flattened body; those living in trees are long and slender with a prehensile tail while burrowing snakes tend to be compact. Snakes are found in a huge range of colors, from bright to dull. Brightly colored snakes are usually venomous, their coloration serving as a warning to predators, while dull colored snakes use their coloration for camouflage. Some snakes mimic the color and pattern of venomous snakes.
The head presents the eyes and the jaw. Interestingly, snakes’ eyes are also covered in scales, clear ones, also known as brille, as opposed to movable eyelids. They are always open, and so, when the snake wishes to sleep, it will close its retina or bury its face among the folds of its body. When it comes to sight, there are great variations across species. Some have good vision (e.g. arboreal species), whereas others are barely able to distinguish light from darkness (e.g. burrowing species). Generally, though, snakes have adequate, yet not excellent, vision, which they use mostly to track the movements of prey. Nocturnal species will have slit pupils, while diurnal species, will have round pupils.
Some species of snakes, such as vipers, pythons, and boas, have infrared-sensitive receptors on their snout, mainly on the side of the head, in grooves located between the nostrils and the eyes, and on the upper lip, which allows them to see the radiated heat of warm-blooded prey. While these species will use these sensors to locate prey, others will rely on scent. Using their forked tongue, which they keep constantly in motion, they collect airborne particles, but also particles in the ground and in the water, depending on the environment in which they live and the place in which they are, thus getting a sense of smell and taste at the same time, which they then pass on to the vomeronasal organ (also known as Jacobson’s organ) in their mouth.
With its skull being made out of an unusual number of joints, a snake’s jaws are very mobile, capable of separating widely, which gives the snake the ability to swallow prey much larger than its head.
A snake’s vertebral column can consist of anywhere between 200 and 400 vertebrae, in some species even more. Its anatomy is also adapted to this elongated shape of the body, with its paired organs laid out one after another, as opposed to side by side. The heart is able to move around, an adjustment that is thought to protect it by accommodating large prey passed through the esophagus and, because all organs need to be long and thin, many species only have one functional lung.
Contrary to expectations, snakes’ skin is not slimy, but smooth and dry. Molting occurs periodically throughout the snake’s life, serving a variety of functions:
- replacing the old, worn skin;
- helping get rid of parasites, such as mites and ticks;
- allowing growth (though this has sometimes been disputed).
While old snakes may only shed once or twice a year, younger snakes have been known to do so around 4 times a year.
Snakes can be found on every continent, with the exception of Antarctica, as well as some large islands, such as Ireland, Iceland, Greenland, Hawaii, and some small islands of the Atlantic and Pacific Oceans. Sea snakes are highly prevalent in the Indian and Pacific oceans.
Snakes are ectothermic, meaning that they rely on environmental heat sources in regulating their body temperature, which allows them to operate at ‘economical’ metabolic rates. This, however, also means that they are heavily dependent on the environment. As such, in cold regions, where winter temperatures drop more than can be tolerated, snakes will brumate – that is, they will remain awake, but inactive. This can be done in a variety of places, ranging from burrows, underneath rocks, inside fallen trees, etc. Some species of snakes may even aggregate in large numbers and brumate together.
Depending on the environment in which they live, different species of snakes will have developed different modes of locomotion. Most notable are:
- lateral locomotion: the sole mode of aquatic locomotion, as well as the most common mode of terrestrial locomotion, where the body of the snake flexes to the left and to the right, resulting in a wave-like motion;
- sidewinding: used in environments that do not present the irregularities that snakes must push against in order to achieve lateral locomotion, such as sand dunes or mud;
- concertina movement, occurring in snakes and other legless organisms that consists of gripping or anchoring with portions of the body while pulling or pushing other sections in the direction of movement;
- rectilinear movement;
- arboreal movement, which actually includes several modes of locomotion, depending on the species of the snake, as well as the tree.
Breeding and dietary information about snakes
When it comes to reproduction, all snakes use internal fertilization. Some species (especially those living in cold climates) are even ovoviviparous, retaining the eggs inside their bodies until they are nearly ready to hatch (e.g. the boa constrictor, Boa constrictor; the green anaconda, Eunectes murinus), in the meantime feeding them from a placenta. Once the eggs are laid, most species abandon them, with some exceptions. The king cobra (Ophiophagus hannah) will construct nests and remain in the vicinity, and most pythons will coil around the eggs and remain with them until they hatch. There are also some species of snakes that reproduce by facultative parthenogenesis. This means that they are capable of switching from a sexual mode of reproduction, to an asexual mode, growing and developing the embryos without fertilization.
Most species are non-venomous, but those that do carry venom primarily use it in hunting and not in self-defense. There are, however, as is well-known, species that possess venom strong enough to cause painful injury and even death to humans. The category of ‘venomous’ snakes includes 3 families:
- Elapids: cobras (including king cobras), kraits, mambas, Australian copperheads, sea snakes, coral snakes;
- Viperids: vipers, rattlesnakes, copperheads/cottonmouths, bushmasters;
- Colubrids: boomslangs, vine snakes, mangrove snakes, and various other species of tree snakes. (It must be noted, however, that not all species of Colubrids are venomous).
Snake venom is actually modified saliva: a mixture of neurotoxins, which attack the nervous system, hemotoxins, which attack the circulatory system, and numerous other toxins, which affect the body in different ways, as well as an enzyme called hyaluronidae, which ensures rapid diffusion of the venom. The actual proportions will depend on the species; often, the venom will be prey-specific, especially in the case of species that use it primarily in hunting.
The venom is delivered through fangs. Interestingly, depending on how much the species relies on venom, the configuration of the fangs will be different. In aggressive species, which use venom in hunting, the fangs will be hollow, which will allow for more efficient venom injection, whereas in species that use venom only in self-defense, they will have a groove on the posterior edge, which will allow them to channel small amounts of venom into the wound. Furthermore, depending on the position of these fangs within their mouth, at the front or at the back, some snakes will need to bite their victims, while others will merely need to “stab” it.
Predators of snakes include certain birds, mammals, as well as other species of snakes. As mentioned briefly above, a snake’s primary method of defense is its venom. Some hunters, however, have developed resistance and even immunity to certain venoms, reducing a snake’s defense abilities to, basically, how fast it can run away. Thankfully, because the underside of a snake’s body is very sensitive to vibrations, it can sense approaching animals by detecting the vibrations they cause in the ground, and can get away from predators before these have detected it.
All snakes are carnivorous, feeding on small animals, such as birds, eggs, fish, frogs, insects, lizards, small mammals, snails, other species of snakes. Apart from the environment, the only major factor that has an influence on the type of prey that snakes prefer is their size. This is because snakes cannot chew, so they have to swallow whole whatever they want to eat.
The process of digestion is an intense activity that requires a lot of energy, especially if the consumed prey has been large. This is the reason why, when digesting, snakes will enter a dormant phase. If disturbed, snakes will often regurgitate, otherwise being unable to escape the threat. Interestingly, because snakes are ectothermic, the temperature of the environment plays an important role in digestion, the ideal temperature being around 30 degrees Celsius.
Snakes as pests
Nonvenomous snakes are not a threat to humans. They can bite, cause tissue damage, and, in some cases, can even cause infections, but that is not the way most encounters with such snakes end. Furthermore, even when it comes to venomous snakes, most species will rather avoid contact with humans; unless startled or injured, the chances of being bitten by one of these species are quire rare.
However, species of snakes that are both venomous and aggressive pose a serious threat to humans. Documented deaths are uncommon, but nonfatal bites often result in the need of amputation of a limb or part thereof, especially in cases where medical attention is not given in time. The most common and most effective treatment is anti-venom: a serum made from the venom of the snake, which can be species-specific (monovalent) or otherwise (polyvalent). Though many people fear them, snakes are a very important part of our ecosystem. They help control pest populations for a variety of animals because they eat mice, slugs, grubs, insects, and other pests and they can be food for other wildlife such as hawks.
Whether snakes already populate your land or there’s a worry they might, a couple of steps can help prevent a long-term stay. First, remove as much of their preferred habitat as possible. Snakes like something to hide in like wood piles, piles of debris, high grass and overgrown vegetation. If such harbourage is removed, snakes will relocate. Second, seal any openings leading into structures such as homes, outbuildings, garages. To be able to prevent their return or to fight of an infestation, visit our related articles as you will find more details regarding ways of preventing and also of getting rid of snakes.