Are Hognose Snakes Venomous?

Executive Summary:

  • Yes, hognose snakes are venomous.
  • No, hognose snakes are not dangerous.
  • Venomous does not (necessarily) mean dangerous.

Which hognose snakes are we talking about?

For the purpose of this discussion, “hognose snakes” include Heterodon in North America, Lystrophis in South America, and Leioheterodon in Madagascar. It does not include hognose pitvipers (Porthidium) in Latin America, or any other viperid or elapid.

The three genera of hognose snakes are all members of the family Colubridae, the taxonomic junk drawer of “typical” snakes, whatever that means. With a few notable exceptions, colubrids are harmless to humans. Although a surprising number of them are rear-fanged, only a handful are of any medical importance whatsoever to people.

What’s the problem?

The debate in online reptile forums over whether hognose snakes should be considered venomous is surprisingly common. Quite a lot of the debate seems to stem from a need among reptile enthusiasts to reassure the general public (and sometimes each other) that hognose snakes present no threat to humans, which is correct. There is a widespread concern — and not without justification — that if hognose snakes are labeled “venomous,” people may be more likely to kill them and lawmakers may be more likely to place restrictions on keeping them. Both of these things are, unfortunately, probably true. (At least one US state prohibits keeping Heterodon, having failed to make an intelligent distinction between “venomous” and “dangerous.”) So to discourage these kinds of irrational overreactions, the herp community is eager to make it clear — correctly — that hognose snakes are harmless.

This earnest desire to paint these adorable, good-natured snakes in the best possible light leads to some word games and mental gymnastics, and some beliefs that simply aren’t connected to reality. For example, advocates continually characterize symptoms associated with hognose snake bites as “allergic reactions,” insisting that venom can’t possibly be the cause. This logic is backwards, for a couple of reasons. First of all, genuine allergy is an immune response, and it can be much more dangerous (not less!) than the effects of a relatively weak venom. I would much prefer to endure the relatively mild effects of a mild venom than have an allergic reaction to it. Secondly, actual allergic reactions to bites from rear-fanged snakes are virtually unheard of.

Another common word game revolves around the insistence on calling what hognose snakes produce “modified saliva” rather than venom, as if that’s a meaningful distinction. It’s not, and it’s silly. Evolutionarily speaking, all venom is modified saliva, and the stuff hognose snakes deliver via their fangs is not ordinary saliva. This is the same kind of strained linguistics that leads the makers of the diabetes drug Byetta (exenatide) to insist that the peptide comes from gila monsters’ saliva, rather than venom. Evidently, “venom” just sounds too scary to be associated with anything we might want, be it a medication or a pet.

All of this is, however, largely a matter of perception management — asserting what we wish were true, regardless whether it’s actually real. I argue that the better answer is to educate people, not to propagate misinformation.

What does it mean to be “Venomous”?

Without getting into the whole poisonous-versus-venomous debate, most definitions of venomous are pretty consistent:

  • “(of an animal, especially a snake) secreting venom; capable of injecting venom by means of a bite or sting” —
  • “(of an animal) having a gland or glands for secreting venom; able to inflict a poisoned bite, sting, or wound” —
  • “producing venom in a specialized gland and capable of inflicting injury or death” —

Venomous Reptiles and Their Toxins defines venom as “A secretion produced in specialized cells in one animal, delivered to a target animal through the infliction of a wound and that disrupts endophysiological or biochemical processes in the receiving animal to facilitate feeding, defense or competition by/of the producing animal.”

There’s an important factor that is not part of the definition of venomous: whether they are dangerous to humans. That has nothing whatsoever to do with whether an animal is, in fact, venomous. Most snakes that are venomous, physiologically speaking, are not medically important to humans, and this is true of all but a handful of venomous colubrids.

So, with regard to whether hognose snakes should be “considered” venomous, it’s not a matter of opinion or consensus; it’s a fact of their physiology. They have specialized glands, known as Duvernoy’s glands, separate and distinct from their ordinary salivary glands, that produce venom. Duvernoy’s glands differ from the venom glands of viperids and elapids in that they are smaller, usually lack a central lumen, and lack well-developed muscles to eject venom under pressure, but nevertheless they are one of several types of venom glands snakes have. And while their venom is not exceptionally toxic to people, hognose snakes are absolutely capable of delivering bites that become symptomatic — although not medically important — in humans.

Hognose snakes have small, faintly grooved fangs located roughly under their eyes, along which venom is delivered. The fangs aren’t hollow, so venom flows along them, rather than through them. Because their fangs are small and not right at the front of their mouths, there’s a persistent belief that they have to chew in order for the fangs to engage what they’re biting. This isn’t quite true. Snakes’ mouths open surprisingly wide, and generally they have no trouble getting their fangs into a prey item or a finger. However, what is generally true is that, without well-developed muscles to eject venom under pressure, it takes some time and chewing to deliver a decent dose of venom. For this reason, with most rear-fanged snakes, a quick bite is a dry bite.

Venomous versus Dangerous

For the purpose of this discussion, the terms “dangerous” and “medically important” mean a threat to life or limb. Thus, bites may be “symptomatic” without necessarily being “dangerous.”

Hognose snakes’ fangs are tiny, they don’t produce much venom, and their bites usually don’t cause significant symptoms in humans, although occasionally they do. So, while hognose snakes are indeed venomous and can deliver symptomatic bites, they are not dangerous.

The Point

The important distinction is between dangerous and harmless, not between venomous and nonvenomous. So while hognose snakes are venomous, they’re still harmless.

Further Reading

  1. Un cas d’envenimation humaine par un colubridé de compagnie, un Heterodon nasicus (A case of human envenomation by a pet colubrid, a Heterodon nasicus)
    French | English (Google translated)
  2. Venomous” Bites from Non-Venomous Snakes: A Critical Analysis of Risk and Management of Colubrid” Snake Bites
  3. Basics of Snake Fangs on Andrew Durso’s unparalleled blog “Life is Short, but Snakes are Long”
  4. First reported case of thrombocytopenia from a Heterodon nasicus envenomation
  5. Venomous Reptiles and Their Toxins: Evolution, Pathophysiology and Biodiscovery
  6. Natural History of the Western Hog-nosed Snake (Heterodon nasicus) with Notes on Envenomation
  7. Effects of Duvernoy’s gland secretions from the eastern hognose snake, Heterodon platirhinos, on smooth muscle and neuromuscular junction
  8. Envenomation from the Bite of Heterodon nasicus (Serpentes: Colubridae)
  9. Venomous bites by nonvenomous snakes: an annotated bibliography of colubrid envenomation
  10. Induced bite from a hognose snake (German, with photos)

Self-immunization with Snake Venom

Few topics in venomous herpetology generate debate as contentious as that around self-immunization. The subject is so divisive and the opposing opinions hurled with such ferocity that it’s the only topic I specifically called out as having “worn out its welcome” in the posting guidelines for The Venom Interviews group on Facebook. (There’s an exception for peer-reviewed research published in credible journals, but I’m not sure that exception has ever been used.) This rule arose as a practical necessity in response to the certainty with which self-immunization discussions descend into loud, angry bar fights that monopolize the group for days at a time. I suppose it’s ironic to have written an article that’s off-limits for discussion in my own group.

I don’t expect this article will change the mind of anyone already invested in an opinion about self-immunization. But since there are a lot of people who are just hearing about it for the first time and are unsure what to believe amidst all the noise, I thought it might be helpful to try to examine the subject objectively, with as little prejudice as possible.

Here are the topics I’ll try to cover:

  • What is self-immunization?
  • Why is the debate so nasty?
  • Does it work?
  • Is there any application for it?
  • Has it produced new discoveries?

What is self-immunization?

In the context of this article, “self-immunization” (“SI” for short) is the practice of injecting snake venom in an attempt to cause one’s body to produce a titer of antibodies sufficient to at least partially mitigate the effects of envenomation by the chosen species.

Some of those who practice SI do so outside the public eye for practical reasons. Others see themselves as scientific pioneers, blazing new trails for science in the tradition of medical self-experimenters like Walter Reed,  Albert HofmannStubbins FfirthAugust BierMarie CurieBarry Marshall, Elizabeth Parrish, and, of course, Bill Haast. There’s also a small subset of practitioners for whom self-immunization is a public spectacle.

Medical self-experimentation has a fascinating and colorful history. Its track record is mixed, producing both important advancements and catastrophic failures, and it has always been contentious. The flaws in evidence collected by self-experimentation are nicely summarized in Wikipedia’s article on the subject:

“Self-experimentation has value in rapidly obtaining the first results. In some cases, such as with Forssmann’s experiments done in defiance of official permission, results may be obtained that would never otherwise have come to light. However, self-experiment lacks the statistical validity of a larger experiment. It is not possible to generalise from an experiment on a single person. For instance, a single successful blood transfusion does not indicate, as we now know from the work of Karl Landsteiner, that all such transfusions between any two random people will also be successful. Likewise, a single failure does not absolutely prove that a procedure is worthless. Psychological issues such as confirmation bias and the placebo effect are unavoidable in a single-person self-experiment where it is not possible to put scientific controls in place.”

Self-immunization differs from most other instances of medical self-experimentation in that it is not performed by medical professionals. At present, SI is performed, apparently exclusively, by people without formal education in medicine or immunology, and this is evident in some fundamental flaws in their approach — the absence of things like baseline measurements, controls, double-blind trials, etc. The seriousness of these flaws seems to be underestimated or ignored by practitioners, and there appears to be little clarity around how hypotheses are formed and tested, how data are collected and interpreted, and how conclusions are drawn. By any measure, it’s a stretch to characterize current SI practices as “citizen science.”

Why is the debate so… venomous?

Aside from the issues related to SI directly, the nature of the debate itself is fascinating. While many scientists and most herpers seem to have shallow reservoirs of diplomacy, SI is a uniquely potent catalyst for dooming virtually any discussion to vitriolic ad hominem attacks, straw man arguments, and general mayhem.

What is it about this particular topic that makes it seemingly impossible to discuss rationally? After years of observing people argue over SI, it’s often possible to see the triggers that send the discussion off the rails. Opponents of the practice mock its proponents the moment they display some egregious misunderstanding of the science they believe they’re doing. Proponents often invite this ridicule with credulous, uncritical acceptance of half-baked hypotheses until they are disproved — the exact opposite of evidence-based skepticism. Proponents respond with anecdotes, and they deride the opponents as purists, elitists and “haters” (for those still using tween vocabulary), who are impeding progress and stifling discoveries with their silly, uncompromising insistence on rigor.

Each side is openly suspicious the other’s motives. Opponents dismiss the proponents’ claims of “doing science” as a disingenuous cover for desperate, reckless bids to feed their egos with the amazement of admirers who don’t know any better. They are accused of trying to emulate Bill Haast, who had a medical necessity to protect himself 70 years ago, while that medical requirement isn’t the same today.

Meanwhile, proponents reflexively reject these criticisms, claiming that they are nothing but petty jealousy, that the naysayers are secretly bitter than they cannot exhibit such impressive feats of immunity. Skepticism is interpreted as attacks against the practitioner personally or against a personal hero (i.e., Haast). Inevitably, the argument deteriorates into explicit challenges to the opponents’ bravery, masculinity, or general badassery, and all hope for rational dialogue is lost. (Prediction: Responses to this article will follow the same trajectory.)

While the personalities involved and the scientific potential should be two distinct issues, from a practical standpoint, they are hard to separate. The discussion of SI is often overshadowed by the behavior of some (but certainly not all!) who practice it. It’s hard to be a credible public face of something that claims to be a scientific endeavor while, for example, conflating facts and opinions, being unclear what peer review means, misunderstanding what constitutes an experiment or observation, or — and I’m not kidding — challenging people to fights for disagreeing. (Since this article is about the practice and not the personalities involved, I’ve opted not to name names.)

Does it work?

Short answer: It depends.

Whether self-immunization works depends on how you define works. For any sufficiently specific definition of working, it should be possible to let data answer the question. Therein lies a central problem with SI today: As of the time of this writing, objective data on the subject are conspicuously thin, and this is especially remarkable given the extraordinary claims made in its absence. Not only are data lacking, but there’s not much to indicate that data-collection is getting any better.

However, it’s not necessary to abandon skepticism to concede that self-immunization appears to mitigate the effects of some at least some components of at least some venoms to a point where symptoms are reduced, perhaps even greatly reduced, possibly even to a degree that an otherwise potentially fatal bite is survived without antivenom. In the absence of real data, these are bold assertions, but they don’t conflict, in principle, with what’s known about immunochemistry: venom is introduced, B cells make antibodies against it, and those antibodies neutralize the toxins to which they’ve been raised.

Yes, it would be possible to fake the claimed results. For example, one could use venomoid snakes or snakes that were so unhealthy that their venom production was severely compromised. A more rigorous science observer might not be so generous, but I’ll take the risk of saying that I don’t think that outright deception like that is generally what’s happening.

Aside from the anecdotes of individual practitioners, belief in the potential protective capability of self-immunization is bolstered by various studies by the US military, including programs that tested immunization against the venom of Naja naja in humans (1963) and toxoids of Deinagkistrodon acutus, Bungarus multicinctus, Protobothrops mucrosquamatus, P. elegans and Trimeresurus stejnegeri in rabbits and mice (Yoshio Sawai, 1968), often cited as the “habu studies” along with its predecessors involving Protobothrops flavoviridis and Gloydius halys. (Taxons made current for clarity.) Each of these studies reported that immunization had some prophylactic value.

Not all venom toxins are created equal. Perhaps counter-intuitively, the simple toxicity (murine LD50) of a venom is almost certainly less important than what that venom does and how much of it there is. At least some neurotoxins seem to be mitigated by SI, and some toxins that affect blood coagulation might be as well. On the other hand, it seems highly improbable that even a high titer of antibodies would be a match for a massive dose of ferociously cytotoxic (tissue-destroying) venom from a large viperid like Bothrops or Bitis, which would completely overwhelm any antibodies in the tissue at the bite site.

At best, resistance is a better descriptor than immunity, and self-inoculation is a better use of the “SI” acronym than self-immunization.

So the interesting discussion is not so much around the century-old science of whether SI works, but rather whether there’s any legitimate application for it.

Is there any application for it?

Without dismissing it outright, the fact that hyper-immunity might be possible does not automatically make it the best option for protection against envenomation. Whether self-immunization is a good idea should be more a matter of data than opinion, but the dearth of data leaves opinions to fight for themselves.

Is it possible to construct hypothetical scenarios in which hyper-immunity might be useful? Are there situations in which the potential benefits outweigh the risks? Much of the difficulty in answering that question is that there is too little consensus on risks and too little high-quality data on the benefits.

The known risks are not trivial. They include the things we know venom can do, like cause kidney, liver and brain damage. How much damage can it do in tiny doses? Unknown.

There’s certainly the risk of miscalculating the dose, and this error has landed a handful of aspiring self-immunizers in the ER. As far as I am aware, it has not yet landed any in a grave, but that’s more a testament to their doctors’ heroics than to the safety or predictability of the practice.

There’s a risk of taking a more-severe-than-expected bite, overestimating one’s immunity, delaying treatment, and realizing too late how bad the bite was. Delays in treatment could easily lead to more complicated treatment, a longer recovery, and a higher probability of permanent injury, like loss of digits or worse.

There are other risks, like allergy, abscess, and bacterial or viral infection, and quantifying those risks is essentially impossible.

So is there any scenario where self-immunization is worth the risks, the pain, and the general unpleasantness of regular self-inoculation?

I know of several cases of venom-collection professionals who work with species for which there is no antivenom available, and in some of these cases, they work with species that can be extremely dangerous. The small handful of people who actually make a living extracting venom have, on average, about one accident every 30,000 to 50,000 extractions. In these cases, I could understand if these people reasoned that the potential benefit might outweigh the risk. However it is notable that none of those in the major private labs have chosen to self-immunize. All of the major private venom labs in the US — those with a statistical certainty of being bitten — opt for rapid antivenom rather than self-inoculation. Even in those instances where envenomation does happen, there is no clear evidence that the risk:benefit of SI is superior to rapid, well-rehearsed emergency response.

The situation Joe Slowinski faced on expedition in Myanmar is also cited as a possible application. Joe was surveying a remote area, days from medical care, when he was bitten by a small krait (Bungarus multicinctus). The team’s plan to equip themselves to manage such an accident fell apart on arrival in the country, and they decided to press on with the expedition regardless. Despite their heroic efforts, Joe’s team were not able to save his life, and he died the next day. Would self-immunization have saved him? There’s no way to answer that with any certainty. Some have cited Complete and Spontaneous Recovery from the Bite of a Blue Krait Snake (Bungarus Caeruleus) (1955) about Bill Haast’s survival of envenomation by a blue krait to suggest that it could have. But even if that were true, Slowinski’s situation was exceptional in every conceivable way, and it would be difficult to argue that self-immunization under his unique circumstances is a basis for more general application.

There are also cases where antivenom exists, but the person is allergic to it. Is self-immunization a solution in these cases? Again, that’s hard to say, but hospitals are equipped to manage anaphylaxis, and they are infinitely more rehearsed at doing that than they are at treating envenomation, especially exotic envenomation, deliberate or otherwise. It’s tough to make the case that self-immunization is the best way to manage these cases.

Each of these scenarios is highly unusual, and even for those cases, at the very least it would be reasonable to involve an immunologist with the training and expertise to direct and monitor the process.

So while there might be some theoretical application under some truly exceptional circumstances, in practice that’s not how SI is being used. More often than not, it’s being done to facilitate unnecessarily risky handling and demonstrate the ability to withstand intentional bites rather than protect against accidental ones.

There is a fatalistic — but patently wrong — saying among some amateur herp enthusiasts about being bitten that “it’s not a matter of if, but when.” This is simply false. There are well-established tools and techniques for safe, hands-off maintenance of venomous collections that reduce the risk of envenomation to nearly zero. There are plenty of examples of people who have worked with venomous snakes for 30 or 40 years (and more) without ever being bitten. There is no reason to consider accidents inevitable. They’re not. Therefore, SI as protection in the context of general husbandry is insurance against risk-taking that isn’t necessary to begin with. It is the herpetological equivalent of buying expensive, unnecessary insurance against your own drunk driving.

Dr. Bryan Fry summed it up nicely: “Indeed for most of the people self-immunising, a significant portion of their risk of envenomation comes when milking the snakes to obtain venom for self-immunisation. Circular logic at its finest.”

Ultimately, it’s hard to imagine any problem for which self-immunization is the best available solution or preferable to passive immunization with antivenom. The practice boils down to taking significant risks for benefits that are almost certainly unnecessary.

Are there other benefits?

Short answer: None have been demonstrated.

“The plural of anecdote is anecdotes, not data.”
— Dr. Bryan G. Fry

Beyond resistance to envenomation, SI discussions are riddled with wishful thinking and questionable claims about the supposed health effects of injecting venom. It’s easier to be unequivocal about these claims: There is no evidence whatsoever that the human body can somehow accept whole venom — a biocidal cocktail that evolved to kill things — and by some unknown mechanism, magically transform it for its own benefit. There is no support for the assertion that whole venom provides any health benefits whatsoever, either generally or as a treatment for any specific condition. (Immunotherapy with bee venom is beyond the scope of this article, but it’s a whole different process with different objectives.)

A popular response to this objection is something like, “But you can’t prove it doesn’t work!” Sorry, that’s not how evidence works. It’s actually the opposite of how evidence works. It is nonsensical to assert that venom might have <whatever> effect unless there’s some evidence that it actually does. This is critical-thinking 101: Absence of contradictory evidence is not evidence that all hypotheses are possible. It has not been proved that I cannot dead-lift 10x my own weight, but it’s not reasonable to assume that I might be able to do it just because ants can.

“But it did <whatever> for that guy!”

First of all, it probably didn’t do <whatever> for that guy. It’s more probable that <whatever> was a coincidence, a wrong observation, or an effect of some other cause that was wrongly attributed to venom. These stories don’t even make good anecdotes, let alone compelling evidence.

The fact that Bill Haast lived to be 100 years old (and reportedly was rarely ill) is frequently cited as anecdotal evidence that self-immunization could contribute to long life and all-around good health, but that’s a tenuous conclusion. Lots of people live to be 100, and none of them inject snake venom. The 2010 US Census reported more than 53,000 centenarians, and it’s probable that their longevity is attributable to well-understood factors like heredity, general health, weight, diet, activity and exercise, lifestyle, hygiene, stress, and community. The fact that one of these lucky, long-lived folks happened to inject himself with snake venom is not compelling evidence that the venom deserves the credit. This is confirmation bias. There are even occasional smokers who live to be 100, but nobody is in a hurry to credit tobacco for their longevity.

Still, there are adherents with unshakable belief that training (or “boosting!”) the immune system with venoms might have beneficial effects, despite the absence of any evidence to support this. Various other ideas — the notion that you can use venom to exercise the immune system like a muscle (a bad analogy), preserve youth, and boost your energy — have no scientific support whatsoever.

Has SI produced any new discoveries?

Short answer: No.

Long answer: Still no. The modern idea of using antibodies to deal with toxins and pathogens dates back well over a century, at least to the pioneering work of scientists like Edward Jenner (1749–1823), Albert Calmette (1863–1933), Vital Brazil (1865–1950), Clodomiro Picado Twight (1887-1944). While antivenoms have been improved and refined over the decades since they were conceived, the basic idea hasn’t changed: challenge an immune system with venom, allow it to produce antibodies, and then use them to treat someone poisoned with a venom those antibodies can deal with. Whether the antibodies are raised in a horse, a sheep, or a person, the basic idea is the same. SI today is doing little beyond re-creating immunologic effects that have been understood for over a century. It has not, thus far, contributed anything really new to the body of knowledge on the subject, and it appears unlikely to do so.

But could it? Possibly. Maybe. Who knows? SI raises some interesting questions. However, as it’s being done today, it makes no progress toward answering the questions it raises.

The Most Common Myths About Coral Snakes


Those of us who work with venomous snakes get a lot of questions about coral snakes, and we find ourselves correcting the same misunderstandings over and over again. The purpose of this post is to address some of the common myths about these colorful little snakes.

Executive Summary:

  • Coral snakes are front-fanged, not rear fanged.
  • Coral snakes do not have to chew to envenomate.
  • The “red-on-yellow” rhyme is not 100% reliable, especially outside the US.
  • Venom toxicity does not correlate very well with “dangerousness.”
  • Yes, antivenom for coral snakes is back in production.

New world coral snakes

Coral snakes are members of a large family of venomous snakes called Elapidae. This is the same family that snakes like cobras, mambas and sea snakes belong to. Members of this family are called elapids, and aside from sea snakes, coral snakes are the only elapids found in the Americas, where there are more than 60 species in three genera: Micrurus, Micruroides and Leptomicrurus.

The US has only three species of coral snakes: the eastern coral snake (Micrurus fulvius), the Texas coral snake (M. tener), and the Arizona coral snake (Micruroides euryxanthus).

Rear-fanged or front-fanged?

Short answer: Front.

A common misconception about coral snakes is that they are rear fanged, but they’re not. One of the things that coral snakes have in common with all the other elapids is that they are front-fanged snakes, just like cobras, kraits, mambas and taipans.

Micrurus fulvius skull

Eastern coral snake (Micrurus fulvius) skull

Elapids are different from vipers like rattlesnakes in that their fangs don’t fold back, so they have to be pretty small to fit inside their closed mouths. In fact, coral snakes’ fangs are so small that they’re actually a little hard to see.

A common assumption is that coral snakes have to chew on you to deliver venom, but that’s not true either. This idea may have originated from the fact that coral snakes bite and hold their prey, which for most species is other snakes. This holding and chewing behavior is common among almost all snakes that eat other snakes, but it probably has more to do with not letting their prey get away than it does with needing to chew to deliver venom.

So, while it’s pretty hard to get bitten by a coral snake, they can deliver a dangerous dose of venom with just a quick bite. And while they are small snakes with small mouths, they can bite pretty much anywhere; they don’t need to get you between the fingers as you’ll sometimes hear. Any exposed skin is all they need.


Short answer: You can’t always trust the “red-on-yellow” rhyme.

Quite possibly the most misunderstood thing about coral snakes is how to identify them, and particularly how to tell them apart from harmless snakes that look similar. There’s a popular rhyme that everyone seems to know that has for decades been a popular way of telling them apart: “red-on-yellow, kill a fellow” and “red-on-black, venom lack.” There are lots of variants of those rhymes floating around, and those might not be the exact ones you’ve heard, but all of the versions have the same idea: that coral snakes can be identified by red bands touching the yellow ones.

In some places, this can be helpful in telling coral snakes apart from species like scarlet snakes and scarlet king snakes and some milk snakes. But here’s the important thing to remember: While the rule might be helpful most of the time, it’s not 100% reliable. There are some important exceptions. For example, in the Southwestern US, there’s a little nonvenomous species called a shovel-nosed snake, which has red and yellow bands together.

Western Shovel-nosed Snake — Chionactis occipitalis

Sonoran Shovel-nosed Snake (Chionactis palarostris) — photo credit: Larry Jones

But that’s not the only exception. Coral snakes’ colors and patterns aren’t always typical. There are conditions like melanism — where the snake is mostly black — or albinism — where it’s lacking black pigment.

Texas coral snake (Micrurus tener; melanistic) — photo credit: Tyler Sladen

Texas coral snake (Micrurus tener; melanistic) — photo credit: Tyler Sladen

Texas coral snake (Micrurus tener; albino) — photo credit: Chris Harrison

Texas coral snake (Micrurus tener; albino) — photo credit: Chris Harrison

Texas coral snake (Micrurus tener; anerythristic) — photo credit: Matthew Morris

There can be regional variations. For example, the coral snakes in the Florida Keys have little or no yellow, which might lead someone to misidentify the snake if they were relying on the old rhymes.

Eastern coral snake (Micrurus fulvius; regional variant) — photo credit: Richard Bartlett

Eastern coral snake (Micrurus fulvius; south Florida variant) — photo credit: Richard Bartlett

And on top of all that, sometimes there are individual coral snakes whose pattern is just abnormal — or what’s called “aberrant” — and in these cases, the rules just don’t work at all.

Micrurus fulvius (photo credit: Dave Strasser)

Eastern coral snake (Micrurus fulvius; aberrant) — photo credit: Dave Strasser

Outside the US, things get much more complicated. Throughout Latin America, there are lots of nonvenomous snakes that look like what we think of as “typical” coral snakes, including a few that have red and yellow bands together. Some of these harmless mimics are very convincing. At the same time, there are a bunch of coral snakes that don’t have the “typical” pattern.

Micrurus mipartitus

Venomous: Red-tailed coral snake (Micrurus mipartitus), Central America — photo credit: Jörgen Fyhr

Neckband Snake (Scaphiodontophis annulatus), Costa Rica — photo credit: Kris Haas

Nonvenomous: Neckband snake (Scaphiodontophis venustissimus), Costa Rica — photo credit: Kris Haas

They may have no red at all, or no yellow at all, or they may have red and black bands together, or they may have patterns that are nothing like any of these! Here are (some of) the different coral snakes just from Brazil!

Coral Snakes of Brazil — credit: Marcus Buononato

Coral Snakes of Brazil — credit: Marcus Buononato

Confused? Don’t worry. There is one rule that always works, 100% of the time, and that’s this: If you’re not 150% positive about what a snake is, it’s best to just leave it alone.

Just don't touch the snake

Just don’t touch the snake

How dangerous are coral snakes?

Short answer: Not as scary as you think, but don’t be stupid.

I won’t tell you that coral snakes aren’t dangerous, because nearly all of them* have the potential to deliver serious — often life-threatening — envenomation. They’re not snakes you need to be messing with unnecessarily. However, they are not by any means snakes you need to be terrified of. Coral snakes bites in the US are rare (only around 100 per year, 70% of those in Florida), and unless you grab one or step on one with bare feet, your chance of ever being bitten by one is close to zero.

The US doesn’t have many snakebite fatalities. Out of roughly 6,000-8,000 venomous bites reported each year, less than one out of a thousand is fatal. (It may actually be closer to one out of every two thousand.) Of the bites from native species that are fatal, virtually all are from pitvipers, primarily rattlesnakes. I could find only two reports of fatal coral snake bites in the US since antivenom was introduced in 1967: one to a man in Florida in 2008 who did not seek treatment, and one to a five-year-old child in Texas in 1970.

So, how dangerous are coral snakes? The answer to that question is not simple, but the discussion is interesting. It is true that coral snakes’ venom is among the most toxic of all snakes in the US, when measured drop for drop. (Only tiger rattlesnakes and type-A mohave rattlesnakes have more toxic venom.) But drop-for-drop toxicity isn’t the whole picture, and in fact it’s probably not even the most important factor. While coral snakes’ venom is very toxic, they produce it in tiny quantities. An adult coral snake might deliver 10 or maybe 15 mg of venom, whereas an adult diamondback rattlesnake might deliver 300-400 mg or more.

To underscore the importance of volume, consider some examples:

  • A honey bee’s venom is in roughly the same range of toxicity as some rattlesnakes.
  • A yellow-jacket wasp’s venom is comparable in toxicity to a gaboon viper’s.
  • A harvester ant’s venom is three times as toxic as a black mamba’s.

In all of these cases, the insect’s sting is nowhere near as dangerous as the snake’s bite, and that is because the volume of venom they deliver is so small. So while coral snakes can potentially deliver a life-threatening bite, the chance of a properly-treated bite actually being fatal is almost nil.

When it comes to the complexity of treating venomous snakebite, the volume of venom is generally a bigger factor that its toxicity. Compared to most pitviper bites, coral snake bites are generally less complicated to treat, have better outcomes, and cause fewer long-term problems.

There is another factor that works in the favor of people bitten by coral snakes, and that is the fact that their venom tends to act relatively slowly. While a pitviper bite will usually begin to manifest symptoms (pain) immediately, bites from coral snakes may not become symptomatic for several hours — often four to six hours or more — after the bite. So while all venomous snakebites are medical emergencies that must be dealt with immediately, coral snake bite patients typically have plenty of time to reach medical care before things start getting really bad.

The situation with coral snake antivenom in the US

In 2008 Pfizer stopped production of the only FDA-approved coral snake antivenom in the US. All of their existing coral snake antivenom is now long past its original expiration date. However, the FDA has tested representative batches of the antivenom each year and extended its expiration another year. So, yes, the antivenom that’s out there still works. However, that supply is dwindling. Pfizer is in the process of re-starting manufacturing of the antivenom. Additionally, there is a new coral snake antivenom from the University of Arizona undergoing clinical trials at several hospitals in Florida. It is hoped that one or both of these antivenoms will be available again by the time the existing stock expires or is exhausted. (For more about this, see “Coral Snake Antivenom” in the bonus clips of The Venom Interviews.)

Update: In October, 2016, Pfizer announced that its coral snake antivenom (formerly Wyeth’s) was back in production and available to order. Clinical trials of the new antivenom are effectively on hold for now.

* Arizona coral snakes of the genus Micruroides are tiny snakes. There are no records of fatalities for that species or, as far as I’ve been able to find, even a very serious bite from one. That said, you don’t want to be the first one, so leave them alone too.

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