I woke up with an itch for the outdoors, so I laced up and hit the road. Half an hour later, I’m 20 yards deep in oak-hickory bliss at my favorite local nature preserve.
But while the trees were fantastic in all of their mid-summer glory, I was really there to see critters.
And as always, I had a specific target in mind.
Rain: A Welcome Reprieve for Wildlife
Atlanta is famously hot during the summer.
You can push a screwdriver into the city’s sunbaked asphalt by early May. By late June, you don’t even have to use the pointy end.
These hellish temperatures may fray human nerves, but they’re a much bigger deal for the animals who call the region home. Birds still fritter about beneath the canopy at mid-day, and invertebrates will continue to keep calm and carry on, but the reptiles, amphibians and mammals will largely lay low. They’ll wait until the shadows lengthen to do what they need to do.
All of this is to say that the current conditions were not ideal for spotting wildlife.
But there was one thing working in my favor: It had rained the entire day and night before. Rain cools everything off, and it tends to stimulate summer-weary animals to move. And this is especially true of snakes – the animals I was most eager to see.
So, on balance, I was a bit optimistic, despite the fact that it was 9:00 AM, and I was already soaked in sweat.
Meanwhile, a tiny snake was already lurking on the forest floor, ready to change the ways I thought about snakes and storms.
It probably even made me a better skeptic.
Acquainting Yourself with a Common Critter: Copperhead Characteristics
I am fond of the vast majority of the animals running through southeastern forests. From the red-backed salamanders lurking under decaying logs to the redheaded woodpeckers hammering away in the canopy, I love them all.
But we all have our favorites, and on this day, I was looking for one of mine — the copperhead.
Copperheads are relatively small pit vipers; the largest males may slightly exceed 4 feet in length, but most adults are in the 2- to 3-foot range. The young, which are normally born in the late summer or early fall, are tiny, measuring about 8 to 12 inches in length.
Highly adaptable animals, copperheads will eat virtually anything they can. This means that in addition to rodents, lizards, frogs and other typical snake fare, they also consume cicadas, caterpillars, salamanders, other snakes and birds.
Copperheads actively prowl for food at times, but often, they simply curl up in the leaf litter and wait for prey to walk by. Clad in some of the most effective camouflage in the animal kingdom, they are well adapted for such tactics.
The young even bear sulfur-yellow tail tips, which they will wiggle in a manner suggestive of a caterpillar or worm. When a passing frog or lizard spots the yummy morsel and moves in for the kill, the tables turn. The forest floor springs to life, and the prey finds itself staring down the business end of a hungry pit viper.
Fortunately, copperhead venom normally produces relatively mild symptoms in humans. Deaths from their bites are almost non-existent with competent medical care.
But the venom will still ruin your day, as it causes great pain, swelling and tissue damage. So, bites are definitely best avoided.
I actually witnessed a young lady suffer a copperhead bite in this very park a few years earlier. She made it through the incident with no long-term repercussions, but her parents were faced with a six-figure medical bill.
It’s Simple: Snakes Move Around in the Rain
The tendency for snakes to become active in conjunction with rainy weather isn’t terribly controversial.
The notion appears in plenty of popular books, websites and articles. For that matter, zookeepers, PhDs and others wise in the ways of snakes often treat the premise as a basic fact.
My own experiences supported the contention as well. While I never collected or analyzed any data on the subject, I have found snakes crossing roads, trails and driveways during heavy rains dozens of times.
But the problem is, when you dig into the available research, things get more complicated.
Let’s be clear: There is plenty of evidence backing the assertion that snakes become more active in rainy weather.
Sea kraits — some of the most interesting snakes in the world and the subject of a 2008 study – provide a great example. This species clearly alters its behavior to take advantage of showers.
True sea snakes spend their entire lives in the ocean, but sea kraits are amphibious; they split their time between the land and rocky islands in the sea.
But despite being well suited for a life largely spent in saltwater, sea kraits require fresh water for drinking.
This is no small problem for snakes who spend their lives surrounded by saltwater. Most of the islands and shorelines they inhabit are devoid of rivers or lakes.
But fortunately for sea kraits, freshwater fills rock crevices along the shoreline when it rains, which provides a lifeline for the snakes. In fact, these rain-filled pools appear to be their primary source of freshwater.
However, water evaporates quickly in the hot tropical sun, and splashing waves dump more salt into the pools by the minute.
This means that the snakes don’t have time to waste. So, when it rains, the sea kraits crawl ashore and begin slurping up the water like mad.
This study provides empirical evidence of at least one species altering its activity based on rain, but what about more “normal” snakes, who live in places with plentiful water?
It turns out that several studies document terrestrial snakes increasing their activity levels during rainy weather:
- A 2001 study conducted by Otavio A. V. Marques, Andre Eterovic and Whaldener Endo, studied the activity patterns of vine snakes, terrestrial pit-vipers called jararacas, and a handful of other species native to the rainforests of coastal Brazil. Their data showed that six of the local species did, in fact, move around more during the rainy season.
- Another study involving Brazilian pit-vipers (though this time, it was the common lancehead or fer-de-lance) yielded similar results. M. Ermelinda Oliveira, author of the 2001 study, even reported that the “monthly number of individuals found with TCS did not differ from expectation and was correlated with rainfall but not with humidity or temperature.”
- Christine A. Schlesinger and her colleagues at Charles Darwin University studied a similar issue in 2010. They primarily focused on lizard activity levels, but they collected data on one snake species living in their study area. After reviewing the data collected over several years’ time, they concluded that blind snakes were more active in years with higher rainfall totals.
Taken in conjunction with the consensus among snake keepers and my own anecdotal observations, it would appear that snakes do, in fact, become more active in rainy weather.
Except that they don’t. At least not all of them.
Sorry, Snakes Actually Aren’t Active in the Rain
I neglected to mention one important bit of data produced by the 2001 study of coastal Brazilian snakes.
In addition to the six snake species that became more active during the rainy season, one species was encountered more frequently during the dry season. Four others were equally active in both the wet and dry seasons.
Plenty of other studies have also produced evidence at odds with the hypothesis that snakes become more active in wet weather:
- A 2005 study of Australian tiger snakes by H. Butler, B. Malone and N. Clemann revealed that rainfall did not affect their activities in any significant way. In fact, the snakes were most active when the sun was shining.
- Dennis K. Wasko and Mahmood Sasa studied common lanceheads living in Costa Rica and found that rainfall did not influence their behavior. In fact, the authors of the 2009 study found that lanceheads acted normally in all conditions except “extremely heavy rains”.
Note that the second study is directly at odds with the data collected by M. E. Oliveira while studying Brazilian members of the same species in 2001!
But the most important study (to my mind) was carried out by G. P. Brown and R. Shine in 2002.
During the course of their work, which sought to examine how snake activity levels fluctuated with a variety of environmental parameters, the researchers noted a few interesting and subtle trends in their research subjects. Water pythons, for example, altered their activity levels in conjunction with the amount of moonlight present.
However, the most interesting trend they discovered was the relative lack of weather-associated trends.
Better put by the authors, they explain that “…standard weather variables (temperature, humidity, precipitation, moonlight, atmospheric pressure) are surprisingly poor at predicting the numbers of individuals and species encountered during standardized surveys.”
Nothing But Nuance: Nature Abhors Absolutes
So, having looked at some of the evidence available, it seems apparent that while some snakes do become more active in rainy weather, others become less active or fail to alter their behavior in any meaningful way when it rains.
Why then, is the belief that snakes become more active in rainy weather so widespread, when the evidence suggests behavioral patterns vary widely among different species?
In my case, the reasons are pretty clear: over-generalization and confirmation bias.
The statement “snakes become more active during rainy weather” is simultaneously right and wrong; it is true in some cases and false in others.
The fact is, while snakes all spring from a common ancestor, they are an incredibly diverse group of organisms. And each one has evolved in response to a different assortment of selective pressures. Accordingly, the 3,000-odd living species respond to rain in many different ways.
Honestly, I’m pretty disappointed that I fell victim to over-generalization. I know that different snake species behave and satisfy their biological needs in different ways. For that matter, I know that different populations within species often exhibit their own unique strategies and adaptations.
But I’ll forgive myself for falling victim to confirmation bias – we all do.
Confirmation bias is the tendency for people to embrace evidence that supports their hypothesis while ignoring any evidence that conflicts with their previously drawn conclusions.
In this case, I thought that snakes became more active in rainy weather, so I remembered all of the times I encountered a snake when it was raining. Conversely, I ignored all those other times when it was raining, but I didn’t encounter a snake.
It is also likely that I read and retained more literature supporting the correlation than I did things that refuted it. Subconsciously, I favored the information that confirmed my belief.
So, as you move forward, be mindful of the effects overgeneralization and confirmation bias can have on your thoughts and actions.
Just be sure you don’t step on your confirmation bias.
It may sting.
I’d only been hiking for about 20 minutes when I saw the beautiful little beast.
It was about 50 yards in front of me, slowly wiggling across the wet, dark mulch covering the trail. The contrast between the mulch and the serpent was significant, but it was the young snake’s movement that caught my eye.
After completing an impromptu rendition of the “I found a copperhead!” dance, I regained my composure and began snapping as many photos as I could.
I filled a memory card with hundreds of essentially identical photos and then ushered the little bugger off the trail with a stick. Hopefully, the then-tiny pit-viper is still prowling the forest to this day.
This particular animal looked too small to be a yearling; I imagine he or she was a few weeks old at best. It was a little early in the year for copperheads to be giving birth, but the previous winter was very mild, and spring arrived quite early. This may have helped the snake’s mother get a jump on things.
Chance encounters like this will drive you crazy. They can also alter the way you think about things.
If I’d caught a few more green lights on my way to the forest, I probably would have trotted right by the snake, who’d still have been lurking out of sight deep in the trail-side vegetation.
On the other hand, if I’d enjoyed a second cup of coffee, the serpent would have undoubtedly finished crossing the trail and slipped into the vegetation on the other side by the time I’d passed through.
Either way, the timing was certainly serendipitous.
Who knows how alternative eventualities would have influenced my thinking about snakes and storms.
Had I not gone down a rabbit hole of research on the issue, I’d have likely added one more anecdotal arrow to my quiver of confirmation bias. But if I’d missed the snake entirely, I probably wouldn’t have thought much about the hike at all.
I have yet to find any rigorous studies examining the relationship between copperheads and rainy weather. But one thing’s for sure: After recognizing the roles over-generalization and confirmation bias played in my prior thinking, I will try even harder to avoid them in the future.
And if I’m ever asked whether rain influences copperhead activity levels, I’ll respond with a confident “I don’t know.”
Header image from Pixabay.