July 22, 2009
Jim Chestney has been chasing timber rattlesnakes for almost 40 years. It started out as something he did for fun. Now it’s his job.
Today, Chestney and his colleagues from the Pennsylvania Fish and Boat Commission, which oversees snake management, are out on the base of a mountain in northcentral Pennsylvania, looking for snakes.
“Up through the brush I can see open sunny rocks,” Chestney says. “That's what's called a gestation area—where pregnant females go to spend the summer. We're about 200 feet away from the den right now. I can't see because the underbrush is so thick with black huckleberry and laurel.”
It's rugged habitat—perfectly suited to snakes; less so for the human researchers trying to keep tabs on them. But human encroachment on rattlesnake habitat is a big reason numbers of timber rattlesnakes have dwindled to the point where they’ve landed on the state’s list of protected species. Surveys like the one Chestney is doing now—the first in decades—will provide a better picture of just how healthy the remaining populations are.
Chestney and state biologist Aura Stouffer use their long-handled snake tongs as impromptu walking sticks to navigate the Tuscarora sandstone as they climb the mountain. In their backpacks are syringes for drawing blood, as well as micro-chips they'll implant in the snakes for future identification. As they approach a den, Stouffer spots a snake that’s the same pale color as the rock pile it's sunning itself on. She moves quickly to capture the snake with her tongs and places it in a canvas bag so Chestney can process it on the spot. For safety’s sake, they then ease the snake into a long plastic tube.
“She's pretty firm in the back end. That tells me there's eggs,” Chestney says. “She most likely mated last year, and they hold the sperm until June. Eggs will develop and she'll become impregnated and she'll give birth in September.”
She'll deliver live snakes—not eggs—and probably just seven to nine, only one of which is likely to survive.
“They're not real prolific, and that's of course why the females are now protected in Pennsylvania statewide,” he says.
Chestney works quickly to draw blood, inserting a sterilized needle above the rattle. 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 before releasing it. The chip will enable scientists to track the snake's growth and location in future surveys.
Pennsylvania is believed to have about five percent of the nation's timber rattlesnakes, according to the previous survey. On today’s trip, Chestney and his colleagues are visiting the den sites identified in the old survey 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.
“When you put development in, people won't tolerate a rattlesnake crossing their yard. So that has led to the demise of rattlesnake populations in a lot of areas,” Chestney says.
In addition, snakes often travel for miles—on the same routes they’ve followed for decades—in their search for food and mates. They always return 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.
Poaching is also taking a toll since rattlesnakes fetch a high price on the black market. Chestney says they're surprisingly easy prey, especially pregnant females.
“Females will stay together in big open rocky areas and that makes them susceptible to predation. It can reduce the entire population of females with one careless act.”
Chestney says one of the outcomes of the snake study is making new decisions about protecting the snake and its habitat.
“We can maintain and even enhance habitat open to females, so they can continue to use a rock successfully for the next 30 years. One gestation rock can be the difference between a viable den population and a population fizzling away.”
In the meantime, he's trying to change human perceptions.
“People think the rattlesnake is an evil villain up in the mountain and he's going to attack you,” Chestney says. “Once he knows you're there, he's going to take off. He views you as a large predator and just wants to get away from you. But they don't attack people.”
For an update on timber rattlesnakes and the conclusion of the study, check out this story.