the allegheny front

Researchers Track Timber Rattlesnakes

Deborah Weisberg

Air date: 07/22/2009

OPEN: For centuries, the timber rattlesnake has inspired both fear and fascination. Early Colonists put it on their flag, with the words "Don't Tread on Me." Since then, numbers have dwindled to the point where someday the timber rattlesnake may be nothing more than a symbol, though state wildlife biologists are working to prevent that. The Allegheny Front's Deborah Weisberg has the story, the third in our series, "Protecting Pennsylvania's Wildlife."

Weisberg: Jim Chestney has been scouting for timber rattlesnakes for 38 years...

Ambient: Footsteps in brush

Chestney: We'll go down the road a little bit and avoid this thick laurel...so we'll just take off here.

Weisberg: He and state biologist Aura Stouffer start at the base of a mountain in northcentral Pennsylvania where they've surveyed for snakes before.

Chestney: Up through the brush I can see open sunny rocks. That's what's called a gestation area - that's where pregnant females go to spend the summer. We're about 200 feet away from den right now. I can't see cause underbrush so thick with black huckleberry and laurel.

Weisberg: A snake bite once got Chestney life-flighted to a hospital but even that didn't stop him from returning to his passion - climbing up treacherous rockfields to hear this forbidding sound.

Sound of Rattlesnake

Weisberg: Although he once looked for rattlesnakes just for fun, Chestney now works for the Pennsylvania Fish and Boat Commission, which oversees snake management. He and his colleagues are doing statewide site assessments and snake inventories and collecting DNA. Given the terrain, his isn't a job for sissies.

Chesney: It's rugged habitat. You always have chance of falling and breaking a bone or hurting yourself. Footing is anything but steady.

Weisberg: Chestney uses GPS and a compass to locate dens where snakes emerge in spring to sun themselves and boost their metabolism. Pregnant females spend the summer at maternity colonies. Other snakes search for food, and then for mates, traveling for miles on the same routes they've followed for decades. And always returning to the same dens. If development gets in the way or snakes are removed from their habitat, Chestney says they'll most likely die of exhaustion or starvation trying to get reoriented.

Chestney: They have that homing instinct...that affinity...they're imprinted to one den and when you get them outside their normal range they can't find their way.

Weisberg: Chestney and Stouffer use their long-handled snake tongs as impromptu walking sticks to navigate the Tuscarora sandstone as they climb the mountain. (Sound of climbing) In their backpacks are syringes for drawing blood, as well as micro-chips they'll implant in the snakes for future identification. As we approach a den, Stouffer spots a snake the same pale color as the rockpile on which it's sunning itself. She moves quickly to capture the snake with her tongs and place it in a canvas bag so Chestney can process it on the spot.

Chestney: Aattempting to get the snake up the tube. There we go...right up the tube...now we've got the snake tubed. (sound of snake rattle)

Weisberg: With only the snake's back end exposed, Chestney counts the scales between the snake's rattle and its anal vent to determine she's a female.

Sound of counting

Weisberg: But there's another clear indication of her gender.

Chestney: She's pretty firm in the back end...That tells me there's eggs. She most likely mated last year and actually they hold the sperm until June. Eggs will develop and she'll become impregnated and she'll give birth in September.

Weisberg: She'll deliver LIVE snakes not eggs and probably just 7 to 9, of which only one is likely to survive.

Chestney: They're not real prolific and that's of course why the females are now protected in Pennsylvania statewide.

Weisberg: Chestney works quickly to draw blood, inserting a sterilized needle above the rattle.

Chestney: Okay here we go...I'm into the what's called the matrix there...it's a slow process.

Weisberg: Next, he programs a number into a micro-chip the size of a grain of rice and inserts it gently under the snake's skin. It will enable scientists to track the snake's growth and location in future surveys.

Chestney: Now we'll measure her...I'm going to say 32 inches.

Weisberg: Chestney maps the site of this den then returns the snake to the rock where Stouffer captured it.

Weisberg: Pennsylvania is believed to have about 5 percent of the nation's timber rattlesnakes but the last den survey was decades ago. Chestney and his colleagues are visiting those sites and trying to find new ones. Blood samples like the one taken today will help tell them whether snakes in different parts of Pennsylvania share the same DNA. Or if development and road construction are causing populations to become isolated and inbred. Chestney says human impacts are the rattlesnake's biggest problem.

Chestney: When you put development in, people won't tolerate rattlesnake their crossing yard in their summer travels so, that has led to the demise of rattlesnake populations in a lot of areas.

Weisberg: Poaching also is taking a toll since rattlesnakes fetch a high price on the black market. Chestney says they're surprisingly easy prey, especially pregnant females.

Chestney: Females will stay together...big open rocky areas and all pregnant on one rock...and that makes them susceptible to predation. It can reduce the entire population of females with one careless act.

Weisberg:. Chestney says one of the outcomes of the snake study is to make new decisions about protecting the snake and its habitat.

Chestney: We can maintain and even enhance habitat open to females, so they can continue to use a rock successfully for the next 30 years and cut a tree back. One gestation rock can be the difference between a viable den population and a population fizzling away.

Weisberg: In the meantime, he's trying to change human perceptions.

Chestney: People think the rattlesnake is an evil villain up in the mountain and he's going to attack you...Once he knows you're there, he's going to take off, he'll rattle, he'll go under rock, he views you as a large predator and just wants to get away from you but they don't attack people.

For the Allegheny Front, I'm Deborah Weisberg..