The Endangered Timber Rattlesnake

Sep. 11, 2012
Timber Rattlesnake, Crotalus horridus, Scioto Co., OH August 18, 2012

Eastern America's Fading Music - Castanet of the Woods

by Nancy Stranahan - Arc of Appalachia Preserve System

                                                                                 Photo Courtesy of Wild Ohio

I remember the first time I saw a timber rattlesnake. I had recently lost any chance of being popular in high school when I came out of the closet as an avowed lover of herps. It was hard to say what I loved the best among them - the wondrous native lizards and newts, turtles and frogs - but certainly snakes were among my favorites. I held all my cold-blooded friends in great esteem – the gentle arboreal black snakes, liquid-flowing green snakes, diminutive ringnecks, shining milk snakes, and the aloof racers that moved like the wind and didn’t suffer fools gladly. They all felt as innocent, strangely dry, natural and earthy as a handful of rocks. And every bit as beautiful as semi-polished stones. As far as I was concerned, there weren’t nearly enough of them in my corner of the world. I wasn’t prepared for the energy of my first encounter with a timber rattlesnake, one of only three poisonous species historically found in Ohio – all of them now quite rare, and two species endangered. I was only 18 years old at the time, which dates this memory as occurring a full forty years ago. Lying before me – through the scratched glass of a plexi-glass window – was a snake of a different "timbre." Its midnight-brown and mustard-gold keeled scales swirled in front of my eyes, a strategy that had evolved over millions of years to disrupt the mammalian eye’s ability to note boundaries. "Right there is where the leaf litter stops, and there is where the snake begins," is the perception the snake’s patterns strive to confuse. In the snake’s subtle shadings, it spoke of the forest floor – of shadows, patchy sunlight, rich earthy loam, and decaying leaves. There was a feeling of stillness about its body, as if it were almost as unaccustomed to movement as a fallen log, while the non-reflective matte of its large scales looked as rough as bark. I saw something noble and elegant its cat-like vertical pupils and the heaviness of its resting head, improbably large compared to its delicate neck and large-girthed body. Above all there was a feeling of distance and inapproachability. The forest ecosystem in which it evolved was at least 35 million years old, arguably even older. The timber rattlesnake had shared this forest with its co-evolving mammals for unknown eons, but only alongside humans for the last 16,000 years or so. The poison in its glands had arisen in a world absent of primates, both human and ape. For the vast proportion of its existence, this species has had no need for humanity. But now, if it were to survive the next few centuries, it desperately needed human advocates. The man with the snake lifted the lid of the cage and the serpent suddenly became alert and tense. It lifted its head, and its tail went vertical. The hollow tail segments begin to rattle like a castanet. It was an ancient sound, a message of warning yet one surprisingly pleasant to my ears. I had never before heard a rattler, but I was familiar with the musical instruments it had inspired. In my mind, this timber rattlesnake was not just of the forest, but in some turn of my thinking it WAS the forest, or at least a part of it. Seeing it separated from its tiered and pillared world, lying there in that tiny cage, destined to go who knew where, to adjust to domesticity or not, I felt the prescience of greater environmental tragedies of which I was yet to learn. But the seeds of my future vocation of land preservation – not to blossom until a full twenty two years hence – were partially sown in this animal’s presence. Today, thanks to research done on the timber rattlesnake by a number of devoted scientists across the Eastern Forest, we know a lot more about timber rattlesnakes than in the era of my first encounter. We know why, for instance, the species is doing so poorly. Their problems throughout the Eastern Forest began soon after the arrival of European immigrants and the iron plow. Few rattlesnake dens in Ohio lasted long after statehood was declared in 1803. As the forests were cleared for agriculture, rattlesnakes and farmers mixed like oil and water. Timber rattlesnakes are delicate creatures that live on the knife edge of an extremely meager calorie reserve. Their prey is opportunistic, but among the rodents, they commonly eat young gray squirrels, flying squirrels, white-footed mice, and chipmunks. How does a grounded reptile catch an aerial squirrel? If the life of rattlers could represent one human virtue, it would be patience. When hungry, a timber rattlesnake slowly flicks its smell-sensitive tongue at its surroundings until it discovers a fallen log actively serving as a rodent trail. Even a squirrel prefers to double his speed along a smooth log runway than to hop over obstacles on the forest floor. If the rattlesnake approves of the species at hand, and determines the trace is active, it coils up next to the log, rests its head on the curve of the bark, and waits… and waits. It can wait for up to a week in this ambush pose, never moving at all. Sometimes a chipmunk or a deer mouse flashes by and the rattler strikes and misses. But when the hapless rodent finally makes a fatal dash down the log, it finds itself suddenly punctured by two fangs that can hinge forward with special muscles. Punching the rodent like two hypodermic needles, the hollow teeth rapidly inject a dose of poison. It all takes place in a fraction of a second. The victim usually dies within a few minutes, and is not approached by the snake to swallow until it is safely dead. You could say this predator’s artful assemblage of food-gathering organs, including infrared detectors, constitutes a definite strategy for conflict avoidance. As a viable species, the timber rattlesnake, Crotalus horridus (literally the horrible castanet), is in serious trouble. In almost every state within its original range, it has protected status, but state regulations haven’t been able to halt its continued decline. In Ohio, populations are just barely hanging on. You can still find them in small numbers in four state forests in southern Ohio, and they may already be doomed in half of those four. The situation is even more severe in Indiana and Illinois. The key to timber rattlesnake success is the security of their communal winter den sites. Den sites must have a nearly perfect assortment of features in terms of directional exposure, elevation, moisture content, rock presence, looseness of soil, and degree of slope. Some elements of the environment a mammal is able to create with its own body, or designs with its nesting constructions, have to be found ready-made in the exterior environment of timber rattlesnakes – and such dens aren’t easy to find nor replace. Consequently, timber rattlesnakes have been found to be extremely loyal to the den sites in which they were birthed. If removed from that site, or if that den is destroyed, they burn up survival calories trying to re-locate it. During the summer season, rattlesnakes don’t often move more than a mile or two away from their den site, so in every sense of the concept, their winter den is the geographic axis of their world. Resting on such a slim calorie budget, timber rattlesnakes are slow reproducers and are thus slow to respond to catastrophic drops in their populations. In a world without mowers and automobiles, adults could be expected to live 25-50 years. A female is six years old before she can produce her first set of live young. After that, females only have enough calorie excesses to give birth once every four years, producing only 6-10 babies at a time. The expectation that each of those babies will live more than five years is only one in fifteen. If you put all this data together and do the math, a timber rattlesnake den has to have a minimum of thirty snakes in order to have a chance of being sustainable. A couple hundred individuals would be a lot safer. When’s the last time you walked through the woods and found a den of thirty rattlesnakes? Meanwhile, researchers are racing to learn what rattlesnakes need in order to survive. We now know they probably do best in mature oak-hickory forests, where mast crops are present to support high rodent populations. They need immense undisturbed forest tracts where their dens can stay secret from unethical snake collectors and people who intend harm. They apparently don’t do well in clear cuts of any forest type. Presumably they need forests with enough age and structure to provide sufficient fallen logs on the forest floor for rodent runways. The landscape must include, of course, ideal den sites. Perhaps you’ve already deduced, like we have, that the missions of the Arc of Appalachia, when applied to the right geography, in juxtaposition with the larger state forests that have so far kept the species going, could be of great benefit to the timber rattlesnake. It is the Arc’s mission to bring the past back to life, primarily in terms of historic natural landscapes, and secondarily in terms of remembering the ancient peoples who once called the Eastern Forest their home. By protecting and restoring habitat for the oldest natives of the Eastern Forest – those of tooth, claw and rattle – eras of human history can be remembered in the context of a living landscape, which is each human culture’s cradle and its final resting place, whether nature is consciously honored by that culture or not. Perhaps a culture’s most important legacy is how well it cared for its cradle. We can’t think of any animal more critical to the vision of wilderness restoration in the eastern United States than the timber rattlesnake. Crotalus horridus. Horrible in its majesty. Terrible in its beauty. Window into mystery. Author Nancy Stranahan wishes to thank researcher Doug Wynn for supplying many of the natural history facts in this article. He is completely innocent of any unscientific musings, metaphors, and memories that may grace this piece. Recently retired, he taught high school biology for 35 years, most of that service in the Westerville City Schools. When he wasn’t teaching, Doug devoted much of his remaining time to the study and conservation of the timber rattlesnake in Ohio, work that he actively continues today. He currently remains working as a contract biologist for the Ohio Division of Wildlife.