The Serpent’s Lethality: An Analysis of Snake Venom

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Beautiful yet uncanny and fascinating yet lethal, no animal has managed to attract the fear and wonder of humans throughout history as persuasively as the snake. While some cultures have despised snakes and seen them as symbols of deceitfulness and vindictiveness, others have revered and worshiped the serpents. These varying viewpoints reflect the different ways in which men throughout history have viewed these unique reptiles. Yet what is it about these creatures that captivates the human mind? Is it their unusual design, or their mysterious nature? The answer may just as well lie in the serpents’ fearsome ability to kill. Indeed, snakes are among the most efficient and sophisticated predators in all of nature. Most snakes kill their prey using one of two well known methods. Some snakes possess very powerful coils which they use to wrap around their prey and kill their targets via asphyxiation. These snakes are known as constrictors, and consist of some of the largest and most feared species known to man. However, there exists another common set of snakes which, despite their often smaller sizes, may be considered even deadlier; the venomous snakes. These creatures possess one of the most amazing and lethal hunting mechanisms in the animal kingdom, a trait which has earned them both the fascination of some people and the fear of others. However, many do not understand just how these reptiles use their venom, nor the different varieties of snake venom which exist. This information can be very important, as an understanding of these dangerous animals is necessary when one lives in areas where venomous snakes occur. A proper look into the behavior of venomous snakes and the qualities of snake venom is in order, for it is in the best interests of both man and the serpent.

The banded sea krait (Laticaudia colubrina) possesses a powerful neurotoxic venom which attacks the victim’s nervous system. Photograph Credit: Jeffrey N. Jeffords

Firstly, one might wonder what snake venom even is. It is, in fact, highly modified saliva produced by the snake’s special saliva glands. Snake venom is of a very proteinaceous nature, with proteins constituting 90% or more of the venom’s dry weight. The nature of this venom was first established by Napoleon Bonaparte’s brother, Lucien, in 1843. Upon closer inspection, it becomes clear that snake venom is in no way a simple substance. It is a complex mixture of hundreds, and sometimes thousands, of different proteins and enzymes. Many of the proteins which make up this lethal concoction are actually harmless, with the toxic proteins making up a smaller percentage of the total amount. Furthermore, the makeup of the toxins varies widely from one snake species to another. This allows for the great variety of different snakebite effects. The enzymes present in snake venom often aid in the digestion of the prey animal which receives the snake’s bite, but some of these enzymes enhance or contribute to the toxic effect of the venom.[1] Approximately 20 of these enzymes are known to be toxic. One of them, cholinesterase is used to paralyze the snake’s prey by relaxing the victim’s muscles to the point where they can no longer be controlled properly. Another enzyme, phosphodiesterase, leads to a negative cardiac reaction in victims, most notably a rapid drop in blood pressure. Hyaluronidase is one of the most dangerous enzymes, as it causes other enzymes to be absorbed more rapidly by the victim. These enzymes all cooperate in order to make the snake’s venom as effective as possible, though it should also be noted that no snake possesses every single one of these enzymes. On average, snakes employ six to twelve of these enzymes in their venom.[2] The dangerous mixtures present in snake venom, intricate as they are, allow the snake to bring down their usual prey (and in some cases, much larger creatures) with a single quick strike.

Snake venom is divided into the two broad categories known as hemotoxicity and neurotoxicity.[3] The neurotoxin is designed to attack the recipient’s neurons, or nerve cells, by interfering with membrane proteins and ion channels. The typical effects of this toxin include the loss of motor skills, mental abilities, feeling, and sometimes even consciousness.[4] Sometimes, depending on the dosage of the toxin, breathing difficulties and/or heart failure can result. The effects of hemotoxins are often much more violent in nature, as the venom attacks the circulatory system and muscle tissue, causing excessive scarring, gangrene, permanent disuse of motor skills, and occasionally even leads to the amputation of the affected area.[5] Despite the existence of these separate categories, most snakes actually possess both varieties of toxicity in their venom. However, venomous snakes are classified as neurotoxic or hemotoxic based on which type is predominant in the snake’s venom.[6] Common neurotoxic snakes include cobras, mambas, sea snakes, and coral snakes (all of which are grouped into the family Elapidae), while some of the most well known hemotoxic snakes include rattlesnakes, copperheads, and cottonmouths (these snakes are grouped into the family Viperidae).[7]

The cottonmouth (Agkistrodon piscivorus) is a venomous snake which possesses a hemotoxic venom. Photograph Credit: D. Chalfant/

So how does the snake produce this venom? Despite what some may believe, the venom of the snake is not produced inside the reptile’s fangs. At the base of a functioning fang is a special duct that leads from a large gland behind the snake’s eye. There are two of these glands (one on each side of the animal’s head) and they are actually modified salivary glands surrounded by muscle which, when contracted, forces venom along the venom ducts and right into the snake’s fangs. Near the ends of the fangs, the venom is then squirted out (much like hypodermic syringes).[8]

Yet even more interesting is the number of different ways in which snakes inject their prey with venom. Specifically, there are four different styles of venom delivery among snakes, depending on the serpents’ dentition. Aglyphous, or grooveless, snakes lack grooves on their teeth for venom to run down through. For these snakes, venom drips down the teeth from any available openings. This results in their maxillae becoming saturated with venom when these snakes attack their targets. In order to ensure a successful venom delivery, these snakes must chew on their prey repeatedly. Though time consuming and somewhat risky, this method of envenomation often gets the job done. Snakes within this group include blind snakes and some colubrids.[9]

Opisthoglyphous, or rear grooved, snakes possess long fangs positioned at the back of their mouths. These fangs have grooves running on their lateral sides which help direct venom into the prey. However, since the fangs are located at the back of the snake’s mouth, a large bite is needed in order for envenomation to occur. Opisthoglyphous snakes typically possess rather weak venom which is simply meant to anesthetize their prey in order for the snake to subdue it more easily. All North American species of these snakes are not considered to man, though their venomous bites can nonetheless cause considerable pain for days. Some species found outside of North America can be more dangerous. Two renowned herpetologists, Dr. Robert Mertens and Dr. Karl Schjmidtt, were killed by opisthoglyphous snakes (a twig snake and a boomslang, respectively) after they underestimated the potency of the snakes’ venom and refused medical observation. As such, caution must be practiced with these snakes even though they do not possess the same lethality as other snakes. Many colubrids make up this group, such as the previously mentioned twig snake (of the genus Thelotornis) and boomslang (Dispholidus typus).[10]

The boomslang is among the most dangerous opisthoglyphous snakes known. Photograph Credit: Tanya Dewey, Animal Diversity Web, University of Michigan Museum of Zoology

Proteroglyphs, or front groove, snakes are the third group of venomous snakes. This group consists almost entirely of elapids, such as cobras and mambas. In these snakes, the grooves run so deep that both sides of the grooves overlap each other, forming a channel for venom to flow through. A lumen is located at the base of the snake’s tooth where venom awaits ejection while a discharge orifice lays on one side near the tip of the fang. An adductor, or jaw closing, muscle is attached to the snake’s venom glands so that the glands squeeze out a stream of venom whenever the snake bites down. It should be noted that these snakes possessed fixed fangs which cannot be folded up when not in use. As a result, the fangs are short enough that the snake is not injured when closing its mouth. These snakes also possess the habit of holding onto their prey after the initial bite. Though this tactic could prove dangerous for many other snakes, the neurotoxic venom of proteroglyph snakes works so quickly that the target is simply not allowed enough time to struggle for its freedom. Some proteroglyphs use this deadly venom in rather interesting ways. Cobras such as the rinkhals (Hemachatus haemachatus) and several species of Afro-Asian cobras (Naja sp.) are able to “spit” venom at their aggressors. In reality, the venom is powerfully ejected from their fangs, which possess beveled, circular apertures on the anterior surface just above the tip were the venom is released. African spitting cobras take this curious ability a step further, as their fangs possess spiral grooves which force a spin on the ejected venom, allowing for much greater accuracy. Not only are these snakes dangerously accurate with their venom, the abundance of venom they possess means these marksmen have no qualms with spitting repeatedly at more tenacious enemies; one black necked spitting cobra (Naja nigricollis) emptied its venom glands after spitting a shocking 57 times in only twenty minutes.[11]

The king cobra (Ophiophagus hannah) is an infamous proteroglyphous snake. Photograph Source:

The fourth and final group is that of the solenoglyphous snakes. These snakes possess reduced maxillae and movable fangs nearly half as long as the snakes’ heads. When not in use, the fangs are folded back and upward, against the roof of the mouth. When the snake is about to strike at its target, however, these intimidating fangs are erected outward in a threatening display. These fangs inject venom under great pressure, ensuring the target receives enough of the toxins. The snakes which make up this group (such as the infamous rattlesnakes and adders) are known for their ability to open their jaws nearly 180 degrees from their closed positions. Though these snakes may not possess venom as lethal as that of the proteroglyphs, solenoglyphous snakes possess a deadly combination of large venom storage lumens and extensive compression musculature that allow them to inject large quantities of venom in mere milliseconds.[12] In short, they can be incredibly dangerous when threatened.

The Eastern diamondback rattlesnake (Crotalus adamanteus) is a deadly solenoglyphous serpent. Photograph Credit: Michael Grant

Despite the reputation most venomous snakes possess due to their killing of humans from time to time, most snakes prefer to conserve their venom whenever possible. In fact, the primary purpose of snake venom is to aid in the capture of prey. However, snakes do not possess a wide variety of defense mechanisms. Due to their lack of limbs, they are unable to outrun their attackers and cannot attain the proper leverage for whipping enemies with their tails. Though some snakes have the ability to secrete foul substances to deter their predators and others can feign death, most snakes must rely on their sharp teeth in order to defend themselves. Yet for a venomous snake, biting a predator means wasting valuable venom. Not only does this venom require energy to create, it can also take a fair amount of time to refill. The venom is worth saving for capturing prey, and so some venomous snakes will tolerate a surprising amount of stress before finally striking at their enemy. It is precisely due to this need for venom conservation that many snakes have been designed with so many warning strategies, such as warning colors, hoods, and rattles. These special traits allow these snakes to intimidate any potential predators before having to resort to the use of their venom. Some snakes, however, solve this venom conservation issue in a rather simple way; they just do not inject any venom when they bite their targets. This act is known as a “dry bite.” It works much like a bluff, allowing the snake to scare off the threat while saving its precious venom for its next hunt. It goes to show that even these intimidating reptiles are not as willing to kill anything that crosses their path as people think.[13]

Despite this need for venom storage, the elapid and viperid families are known for using up a massive amount of venom when attacking prey. The Western rattlesnake (Crotalus viridis), for instance, injects its prey (often a mouse) with 300 times more venom than is necessary. Another venomous snake, the inland taipan (Oxyuramus microlepidotus) injects enough of its powerful venom in one bite to kill 200,000 mice. Why this unnecessary waste of venom? In reality, scientists are not sure. However, other snakes in these families are able to meter out how much venom they intend to release into their prey. Therefore, it is likely that the two snakes mentioned are also aware of the excessive amount of venom they are using up. Although some theories have been proposed in order to explain this behavior, none of them are able to explain all cases of this behavior. As a result, the reasons behind this behavior remain a mystery to scientists.[14]

The gaboon viper (Bitis gabonica) is among the largest of the vipers. It possesses a very powerful hemotoxic venom. Photograph Credit: Tanya Dewey, Animal Diversity Web, University of Michigan Museum of Zoology

Each year, nearly 8000 people receive venomous snakebites in the United States alone. Many of these people are bitten because they try to kill a snake or simply get too close to it.[15] When one finds a snake, the best precautions are to examine the encounter. If the snake is far enough away then it is best to simply leave the area. Should a bite occur, however, it is important that one identifies the snake. Different types of snakes possess observable features that are often unique to them. Vipers, due to their large venom glands, have heart-shaped heads. Elapids, on the other hand, possess rather thin heads and often warn the intruder in a noticeable manner before striking. Colubrids are similar in appearance to elapids but often do not give off warnings. Although a snakebite can certainly be a frightening situation, it is important to remember that no venomous snake will attack without severe provocation. One should always be alert for warning signs and wary of where steps are taken in areas where snakes occur. It is also helpful to remember that many snakebites are “dry bites.” Ultimately, the last thing a scared or cornered snake wants to do is bite.[16]

Snakes are among the most interesting animals in this world. Since the dawn of man, snakes have caught the attention of humans in interesting ways. Their skillful killing abilities and unusual design have fashioned them into one of the most notorious of creatures in the eyes of man. Yet, although the history between snakes and mankind is certainly interesting, these magnificent reptiles are not seen for what they truly are in their symbolic depictions throughout the world’s cultures. These creatures are superbly advanced and sophisticated predators possessing lethal abilities that have simply impressed humans throughout the ages. By studying their behavior and design, one can not only learn to appreciate their stunning abilities, but also learn how to live with these incredible animals.

[1] “What is Snake Venom? .” (accessed October 15, 2011).

[2] Ferrer, Ed. “Snake Venom: Pain & Potential of Poison.” (accessed October 15, 2011).

[3] “Venom .” (accessed October 15, 2011).

[4] “Neurotoxin.” (accessed October 15, 2011).

[5] Ferrer, Ed. “Snake Venom: Pain & Potential of Poison.” (accessed October 15, 2011).

[6] “Venom .” (accessed October 15, 2011).

[7] Ferrer, Ed. “Snake Venom: Pain & Potential of Poison.” (accessed October 15, 2011).


[8] “Snake Venom.” (accessed October 15, 2011).

[9] “Venom .” (accessed October 15, 2011).

[10] “Serpentes: Ophidian Dentition.” (accessed October 15, 2011).

[11] “Venom .” (accessed October 15, 2011).

[12] “Serpentes: Ophidian Dentition.” (accessed October 15, 2011).

[13] “Venom .” (accessed October 15, 2011).

[14] Ibid

[15] “Snake Bites.” (accessed October 15, 2011).

[16] “Venom .” (accessed October 15, 2011).

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