How Do Most Snakebites Happen?
A look at the available data and how we present this information
As always, when talking about snakebites, let’s start with the number one thing you should take away from the discussion.
If you see a snake that you cannot positively identify as harmless, simply leave it alone.
The next best advice is to practice situational awareness when outdoors. In other words- pay attention. Seeing a snake before you accidentally step on it or reach near it is important to prevent an injury. You alone are responsible for where you put your appendages (and where your children or pets put theirs).
With that said, let’s talk for a minute about statistics.
If you are one of my regular readers, you may have noticed that my writing is typically more conceptual than statistical. I normally steer away from too many raw numbers. Part of my reason for this is that statistics differ, depending on your source. This is an understandable result of a number of factors, including where and how the data were collected, sampling sizes, and how the data are interpreted. By focusing on consistent concepts, I avoid having to argue over statistical minutia, particularly when those numbers shouldn’t have been the main take-away from the story in the first place.
However, I think it is important to dwell for a moment on the oft-cited claim that, “most snakebites happen when someone is trying to interact with (e.g., capture or kill) a snake.”
I do not teach that statement in my writings. I am very particular with my words. What you will hear me say is that “interacting with a snake increases your chance of being bitten.”
Although similar, those are two rather different statements. The first one is making a statistical evaluation on an epidemiological (medical) matter. That statement could (and should) be examined and argued.
The second statement is purely a point of logic. Even if snakes chased people (they do not), they cannot outrun a human. If you see a snake, you can avoid it. If you do so, you have a zero percent chance of being bitten. Doing anything else, such as trying to kill it, might not result in a bite, but your chances of a bad outcome certainly go up from zero.
Let’s look at the statement that most bites are a result of intentional interactions. Herpetologists sometimes call these “illegitimate bites.” The idea is that the snake really shouldn’t be blamed in these circumstances, even if you’re the type of person who’s going to blame a snake that struck defensively when stepped on (which I think would also be unjustified, by the way).
To be fair, there are studies that suggest intentional interactions cause the majority of bites and other studies state the opposite. I don’t think this is a result of people being sloppy or misleading (though that is always possible) so much as it is that snakebite statistics are a difficult thing to pin down, for many reasons.
- Snakebite is a relatively uncommon occurrence, so sampling sizes will always be small when compared to other health concerns (e.g., automobile accidents, cancer, etc.). This makes it more difficult to draw reliable conclusions.
- Doctors tend to publish accounts of unusual cases, which may have a great deal of educational value to other toxicologists but is not representative of routine bites.
- People tend to lie. If we know full well that we got bitten because we were doing something stupid like picking up a rattlesnake, our ego may get in the way and cause us to claim that it leaped out of nowhere.
- Many people forego treatment. Some do this because they favor alternative medicines (please don’t do that!!). Others would rather be in pain or disabled than be saddled with a large medical bill (also inadvisable from a health perspective). In any event, these bites are not recorded.
- Some studies have tried to piece together second-hand information from patient records where no adequate interview was performed about the circumstances of the bite. Other researchers have attempted to poll random snakebite victims wherever they could be located. These are examples of statistical gray areas, to say the least.
The list of difficulties goes on. Prior to 2013, the largest study available regarding snakebite was AAPCC database characterization of native U.S. venomous snake exposures, 2001–2005. The data for this study was compiled using the Poison Control Centers’ database, which contained very limited information about the bites or their causes. As such, many people familiar with these limitations were rightfully skeptical of the conclusions drawn.
Other, smaller studies have been undertaken on several occasions. Some were compiled by relatively uninterested statisticians (which may not have had toxicological expertise), others were conducted by herpetological societies (which may have had well-meaning preconceived notions as to the frequency of “legitimate bites”), and others for other reasons. All in all, toxicologists saw a need for more standardized data.
In response to these difficulties, the American College of Medical Toxicology established the North American Snakebite Registry (NASBR) in 2013. The purpose of the NASBR is to gather detailed information regarding snakebites, including patient characteristics, clinical effects of envenomation, and response to treatment and outcomes. The strict rule for entry into the database is that the information must be gathered and input first-hand by medical toxicologists directly involved in the bedside care of the patient. This eliminates as many variables as possible from the information, assuring a high degree of accuracy.
While the NASBR is still in its relative infancy, it has amassed a sufficient amount of data to examine. In 2017, an analysis of this data was published, co-authored by The Natural World’s own Dr. Spencer Greene. Data from the NASBR paints a very different picture than the go-to herpetological wisdom that most bites occur when someone is messing with a snake.
During the course of the first four years of the NASBR’s statistical collection, reported intentional interactions represented a mere 19% of snakebites.
Of that 19%, 78 were men, 8 were women, and all sustained bites to fingers, hands, or arms. This is where we would expect such bites to be, considering not many people are likely to intentionally step on a snake without good reason or adequate protection. This figure indicates that the vast majority of bites are therefore a result of people not paying attention to their surroundings rather than trying to kill or capture a snake.
Now, those of you who have been taught that most bites are from people handling snakes may be skeptical at these data. After all, snakes don’t go looking for trouble and venom is biologically costly to produce, so snakes have a vested interest in conserving it. So, let's address two potential issues with this figure of 19%.
First, these are not every snakebite that happened during those years — only those recorded in the NASBR. Second, and in all fairness, what this study proves is that a little less than 1 in 5 people admitted to intentionally approaching a snake. Since we know people are not always truthful, the number of actual interactions could be greater. So, how much higher is the real figure likely to be?
As to the first point: we will never be able to get every detail on every bite, so all we can do is extrapolate from available data. It behooves us, therefore, to build on the most reliable sources possible. In my opinion, the NASBR represents the most reliable and impartial data source currently in operation for the United States. In my experience, many of the people who defend the status quo of most bites being illegitimate tend to do so based on their own anecdotal experience. I think it is safe to assume the NASBR is, at the very least, far more statistically reliable than the standard of “people I know that have been bitten.”
As to the second, trickier point of people lying: we can’t know this one precisely, either. However, it is reasonable to assume that patients who presented with bites to the lower extremities (legs and feet) were more than likely being honest when they claimed to have stepped on a snake unawares or admitted to walking around in the dark wearing flip-flops.
For the sake of argument, though… let’s assume for just a moment that every bite to a finger or hand was intentional and that everyone bitten in those spots was either a part of the 19% or liars. I don’t think this is likely, as many people reach under boards or watercraft, grab for garden hoses, weed their garden, or perform any number of other actions without looking carefully first. Sometimes, this will surprise a snake or cause it to think it needs to defend itself. But, just for fun, how high is that number?
All bites to the hand and fingers total only 41%. This is roughly twice as many bites as the reported intentional interactions, but still a minority of bites as a whole. Again, this should not be confused with the actual number of intentional interactions, but — even if it were — we would still have to say that most bites occur from people not paying attention.
Conclusion
Even if you think that most venomous snakebites happen because of people being cruel or stupid, I hope you will agree that there is enough data to question that position. This is important for a couple of reasons.
- If you are in the practice of educating the public about wildlife topics, you may wish to use language similar to that given above. Rather than quantifying your language, you could simply state that “Trying to harm a snake increases your chances of injury.” This accomplishes the same goal of encouraging people to stop killing beneficial wildlife, but it says it in a way that allows for much less doubt or argument.
- If indeed most bites are caused by people not paying attention, we are doing people a disservice by causing them to think that the snakes they see are their main danger. A snake you see can be avoided — our educational focus should include the importance of situational awareness. This helps people see and avoid more snakes. This is a win-win for humans and wildlife with no real downside.
I hope I’ve given you some food for thought. Intentional interactions with venomous snakes are still a significant problem and we should work to reduce them, but we shouldn’t treat that as the only cause of snakebite.
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