Tracking Timbers

“Everything uses these habitats along the road,” Garrett Sisson explained to me as we drove down a highway in southern Ohio.  I gazed out at the familiar grassy hills and rock cliffs that seemed to turn the landscape into a funnel.  “The deer use the open areas for grazing and the reptiles—the snakes, turtles, and lizards—find the perfect basking sites in these fields.  The wildlife in the area is really taking advantage of the space we have opened up for them.”

I was surprised; Garrett was the first person I had heard say anything positive about a roadway's impact on wildlife.  The impression I had of most roads was one of environmental disaster.  In my mind they were killing machines, luring unsuspecting ectotherms to their warm surface, only to be thoughtlessly crushed by the barrage of speeding vehicles.

Garrett continued, “Both of the gravid female rattlesnakes I have tracked used rock piles along the highway to thermoregulate.  Ironically, the road has created the perfect place for snakes to develop their young.”  Garrett Sisson is a master’s student studying one of Ohio's remaining populations of timber rattlesnakes.

Garrett Sisson showing us one of his rattlesnakes

In the three years of his study, Garrett hasn't lost a single snake to road mortality.  The timbers just don't seem interested in trying to cross.  They come close to the road, but never actually venture out onto its deadly asphalt.  Instead, they use the highway as a tool.  Construction of the road has provided sunny, southward-facing slopes, which the snakes utilized for thermoregulation.  The road is actually helping these State Endangered reptiles to reproduce. 

“It’s not as black and white as it might appear,”  Garrett continued, “There is a give and take here.  If the land could stay habitat instead of becoming an ecological trap, then the highway’s impact could have some real positive effects.”  I had never stopped to question whether a road could actually do anything good for wildlife.  The crushed snakes, turtles, and salamanders I was used to seeing with Charlene and Marcel had convinced me that they were just glorified deathtraps.  

“This is not to say we should pave forest and destroy and fragment more habitat,” Garrett assured me.  “The road mortality is a terrible thing.  What this highway teaches us is mitigation.”  

Mitigation—the action of reducing the severity, seriousness, or painfulness of something.  In the case of this road, mitigation efforts include miles of snake and deer fencing, amphibian tunnels, and underpasses.  These structures attempt to prevent wildlife from getting near the road (or at least provide a way under it).  Some of it works; some of it does not.  That’s what we were trying to figure out.

Roads that cut through habitat are environmental nightmares.  This road's presence probably means a lot of the wildlife that live along its margins are doomed—including Garrett’s snakes.  If we choose to ignore the warnings, then more terrible roads like it will be built.  If we study and learn from it, however, then we won't make the same kind of mistakes in the future.  This road, with all its detrimental effects, could be telling us to change our ways, to become more careful, and to care about the wildlife we risk losing.

I was accompanying Garrett, Dr. Popescu, and Popescu’s former PhD adviser, to look for Garrett’s snakes.  I had briefly seen one of his rattlesnakes a month earlier when I had accompanied him tracking.  Like our turtles, the timbers were fitted with radio transmitters (in this case implanted internally).  Unlike our 30 turtles, however, Garrett had only 3 snakes he was tracking.  This population is so small that he had found just 18 animals during his entire project—twelve of which were neonates too small for transmitters.  Of the five snakes large enough to track, one had died during hibernation and another was killed by a mesopredator like a raccoon or coyote.  Garrett now had just two big females and a juvenile male.

In Ohio, timber rattlesnakes (Crotalus horridus) are listed as critically endangered.  Prior to settlement, timbers were found across nearly 30 counties and on the Lake Erie Islands.  Today, they are found sporadically across just seven or eight southern counties.  Persecution and habitat loss are largely to blame.  Destruction of mature forests with suitable rocky crevices used for overwintering, coupled with unwarranted killing, have reduced their populations to a few broken colonies.  

Timber rattlers are large snakes, growing up to six feet in length.  They are bulky, heavy-bodied serpents with distinct arrow-shaped heads and rattle-tipped tails.  They are distinguished by their two color phases: black or yellow.  The yellow phase is light in color with chevron or lightning bolt crossbands extending from the neck to the tail.  The black phase is dark brown or black with brown or yellow markings and crossbands.  Garrett’s snakes are the black phase, with beautiful dark heads and lighter markings.

Anyone who has worked with timbers will tell you of their gentle disposition.  They take considerable provoking just to entice rattling, let alone a strike.  However, if a timber feels truly threatened, it will defend itself vigorously.  A bite would be serious; the hemotoxic venom is highly potent and can be fatal if not treated.

Venom, however, is an expensive cocktail of proteins to make.  Using this liquid gold on a human—far too large to eat—is a waste.  When feeling threatened, timber rattlesnakes will use every other tactic in their playbook before reverting to striking.  Upon first encounter, a timber will either remain motionless, hoping the threat will pass by, or slip away silently to safety.  If the threat persists, the second line of defense is to rattle.  

Baby rattlesnakes are born with a single button on the end of their tail.  Each time a snake sheds, it deposits a new keratin bead (the same material as our hair and fingernails).  Rattles cannot be used to age a snake as shedding can take place several times in a year and long rattles are prone to breaking.  The rattle is truly an ingenious communication tool.  Snakes have no external ears—they cannot even hear their own rattle.  The rattle’s function is purely cross-species communication, warning large mammalian predators “I am here.  I am dangerous.  Do not get closer.”  Rattlesnakes are practically begging us not to get bitten.

If rattling is not sufficient to warn off the threat, the snake will coil in a characteristic S-pose, and launch a strike nearly a third of its body length.  Even if a snake does bite, it may deliver a “dry bite.”  This is yet another effort to conserve its precious venom.  A dry bite does not result in envenomation—no venom is released.  This strike would merely be painful, not life-threatening.  When encountering any snake, the best course of action is to let it be. Ironically, most envenomations occur when people harass or try to kill snakes for protection.

We hiked up the ravine, over rocks and small crevasses.  Garrett used the same telemetry equipment as Marcel and I.  When tracking rattlesnakes, however, we had to be careful, plodding, and watchful.  It wasn't a race to the finish like it was with our turtles.  Accidentally stepping on a rattlesnake had much riskier implications than did stepping on a box turtle.

As we closed in on the snake, Garrett hiked down into the green briar while our group waited on the trail.  After a moment of searching, Garrett called up to us that he had found her.  Nestled under the tangles of thorns, coiled tightly in the leaf litter, sat Martha.  She was a handsome serpent, approaching four feet in length, with a dark head and thick, light zig-zagging bands.  She sat motionless, allowing our group to surround her without the slightest indication that she had even noticed us.

We examined her elegant patterns and reflected on how easy it would have been to walk right past her, none the wiser.  I was transfixed; it was hard to comprehend that fewer than three feet in front of me sat a venomous viper—the endangered timber rattlesnake, no less.  Garrett also took us to see Nosferatu, an even larger female that was almost solid, coal-black.  She too sat coiled in the leaf litter, a few intermittent tongue flicks the only sign that she was aware of our presence.  I could easily have spent hours staring and snapping photographs of these two snakes.  Garrett had to remind me, “you can’t take them home with you, unfortunately.”  

As I watched the timbers, it dawned on me that they were some of the last remaining snakes of their kind in the state of Ohio.  Repatriation, translocation, and relocation (RRT) efforts have proven unsuccessful.  Timber rattlesnakes exhibit high site fidelity—if moved from their home range or introduced into a new one, they will do everything in their power to return home. Timbers share communal dens for hibernation, which they use their entire lives.  Without a suitable den in which to escape the harsh winter temperatures, a snake will die.  Homing snakes not only face the problem of hibernation, but also the issue of habitat fragmentation.  

Roads have split up countless wildlife populations throughout the state. Their isolating force turns one, interbreeding population into several small, segregated groups. These small groups easily fade out of existence one by one, until sadly, no snakes remain. Hated, misunderstood, unperceived, and fading into extinction—do these beautiful reptiles really deserve this fate?  I don't think so.  A creature with such power and mystique should be our state's pride—a rare woodland jewel.  

Timber rattlesnakes play as important a role in the environment as any mammal or bird. They consume disease vectors such as mice and rats, which serve as hosts for ticks and other parasites.  Infected ticks can transmit diseases like Lyme and Rocky Mountain spotted fever to humans.  Without snakes to reduce rodent populations, ticks and their deadly pathogens run rampant.  Rattlesnakes are not only fascinating and beautiful, but they directly benefit us.  They belong in our woods, and we owe them space and respect.

A new rattlesnake in one of our box turtle sites was unlikely, but not beyond the realm of possibility.  As we hiked out, I imagined how incredible it would be to discover a timber rattlesnake without telemetry.  I would be looking, that much was certain.