Adaptation of the Week – Timber Rattlesnake Camouflage
Image by John White
I've decided to start a weekly series highlighting interesting, strange, or just plain cool evolutionary adaptations. If any of you have suggestions for adaptations that you find particularly interesting, I would be happy to include them.
I'm gonna start off with a species that is dear to my heart, the Timber Rattlesnake (Crotalus horridus). Back in my college days, before moving on to molecular and developmental biology, I was an HHMI undergraduate fellow privileged to spend a summer working under Dr. Steven Beaupre radio-tracking timber rattlesnakes in the Ozark Mountains of Northwest Arkansas.
During the summer, I had about a dozen snakes "assigned" to me. These snakes lived in a large expanse of fairly remote wilderness and it was my job to find each of them on every other day using radio-telemetry, after which I would record a bunch of data on them. One of the most interesting things about the Timber Rattlesnake I learned is that they have largely de-evolved their need or use of their rattle. Granted, this is not really true and most herpetologists and evolutionary biologists would rightly throw a fit for me phrasing it as such; I am using the term de-evolve very loosely. If you pick up one of these snakes and throw it in a bucket (to take it to the lab for example), they will most certainly rattle as if the world is coming to an end.
Watch your step!
Nevertheless, in the wild these snakes are incredibly loathe to make any noise whatsoever, which is quite different from my experiences with diamondbacks in Texas. Diamondbacks that I have found typically want you to know immediately that you are getting close and should get the Hell back. However, I routinely tracked these Timbers and would sit a mere 5-6 feet away from them while taking down their info. By and large, they were content to stare at me tasting my air. The few times they felt threatened, they simply unraveled themselves and slithered away. In fact, in one of the most frightening events of my life (shortened version of the story here), a particular snake's signal bounced strangely leading me to accidentally kick it. Not only did it not strike me (which would have certainly lead to my death under the circumstances), it never rattled. It simply stood erect on its coil, feinting, and doing a great job of looking incredibly terrifying (in response to which my lungs released a bloody-murder scream that I don't believe I can ever replicate).
"Can you hear me now? Good."
The point of all this is that the Timber has taken a different route to self-defense: near-perfect camouflage. More often than not, I would track a snake and know that I was standing withing 10 feet of it yet spend an extra fifteen minutes just trying to see it, even though it was often coiled among the leaves in the open. Many people in the Ozark Mountains can live their entire lives living among Timbers and yet never actually see one in the wild.
Obviously the animal kingdom is filled with myriad examples of camouflage even more amazing than the relatively simple colorations of the Timber Rattlesnake. However, I find the example of the Timber interesting largely because of the public perception of how a rattlesnake should behave (this includes their mild disposition as well as their camouflage).
A Small Example of the Ignorance of (Some) Rednecks
Black Rat Snake (aka "the only good snake is a dead snake")
Today, once again, I witnessed a not-too-uncommon display of ignorance and primitive barbarism in the rural south.
I was driving along a small country back road near my home in North Carolina, listening to a book on CD (no it’s too embarrassing to tell…OK, fine – it was “Twilight” the first novel by Stephenie Meyer about a teenage girl who falls in love with a vampire. Hey screw you – it has amazing character development and who doesn’t like vampire stories?)
Anyway, I was ambling down the road when I saw what I thought might be a snake crossing up ahead. No one was behind me, so I stopped in the middle of the road and got out to check it out. I’m usually the guy who stops to pick up box turtles and carry them across the road – what can I say? I’m a biologist. Sure enough, it was a black rat snake of average length - about 4 feet long – stretched out across the road and moving as if in no hurry. I was glad he had not been run over - usually when I see a snake in the road it’s already dead.
I see a truck pull on to the road a quarter mile down and head right toward us. “Shit,” I think, “This truck will probably aim right toward him.” So I grab the tip of the snake’s tail with the intention of toss him in one quick movement into the ditch. But the snake’s scales were firmly latched onto the blacktop. Plus, he was much quicker than I anticipated. He lashed out at me and coiled into a raised striking position in the middle of the road. He did not find my actions quite as altruistic as I did. Black rat snake bites can be quite painful, considering their row of tiny sharp teeth. I’ve been bitten by one before. They also have a tendency to chew on you once they grab hold. So I backed off.
The truck was not slowing down and other cars were now moving towards us. My car was parked in the middle of the road. I could not see any sticks or anything to handle the snake with, so I decided to leave it to the fates. Maybe the redneck will see that I was just out looking at the snake and will leave it alone, just for my sake (note: I come from a long line of Arkansas/Texas rednecks myself). I get in my car and quickly start it up. I slowly pull forward, and the truck, which had a long trailer attached to the back pulled to a stop in front of the snake. I watched an elderly man get out of the pickup in my rearview. He glanced at the snake, jumped back into the cab, swerved his wheels into the center of the lane, and squashed the snake.
Yet this old man went out of his way to smash a creature that spends its days protecting the man’s crops, or his neighbors. Out here, I’ve seen people swerve to hit opossums, raccoons, snakes, and any other little non-dog-or-cat species.
I saw it writhing over itself - dying - as the truck righted into the lane.
Why do I taste burning rubber?
The black rat snake is non-venomous. It feeds almost solely, as its name implies, on rodents. The land around where we had been is all farmland, the truck was carrying farm equipment, and the man looked himself to be a local farmer.
It makes me sick. I simply cannot understand the mind that would derive pleasure from brutally snuffing out our animal neighbors, particularly considering that these are people that have been raised in their presence. I’m not a hippie PETA activist. And I’m not a vegetarian. In fact, I do experiments on animals for brain research. But the pointless, barbaric smashing of animals with a car for pure fun simply reinforces my own views about large swaths of the human population – namely that in many people, pure barbarism lingers within their psyches, reinforced by superstition, fears of things they don’t understand, and utter unadulterated ignorance.