Biochemical Soul Musings on Nature, Science, Evolution, Biology, and Education

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).