Warning Signs

Scientists are trying to stem the further decline of Pennsylvania’s rattlesnakes
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On the first warm day of May, Jim Chestney cuts through thickets of black huckleberry and laurel and ponders his impending climb to a timber rattlesnake den on a central Pennsylvania mountain.

It’s a toss-​up as to which poses the greater threat — the venomous pit viper Crotalus horridus or its unforgiving habitat. Chestney can attest to both, having suffered a rattlesnake bite that got him “life-​flighted” to a hospital, and having broken several bones from a steep fall. This is rugged, remote terrain and in each of those incidents, Chestney had to drag himself to where he could even call for help.

Still, on this day, he is undaunted — even excited — by the prospect of the task ahead, which is to check on snakes implanted with ID tags during previous surveys, identify new snakes, and assess their conditions and habitats.

It is part of the Pennsylvania Fish and Boat Commission’s most significant statewide timber rattlesnake study, and Chestney, a former snake hunter, is directing field operations. Snakes are in decline in Pennsylvania — which has long been their stronghold — and the agency’s goal is to update its conservation plan.

We’re heading to those open sunny rocks up there,” Chestney said, pointing to an outcropping of boulders of Tuscarora sandstone about 200 yards up the mountain. “That’s where pregnant snakes start appearing at this time of year. It’s a gestation area — a kind of maternity colony — where females gather to warm themselves. Rattlesnakes are gregarious animals.”

Although he has handled snakes for 40 years, Chestney never lost his affinity for their beauty, their mysterious habits and their colorful history. American colonists found them awe-​inspiring, too, and depicted one, coiled and ready to strike, on an early flag with the warning “Don’t Tread on Me.”

Yet despite their fearsome image — or perhaps because of it — rattlesnakes have been killed out of ignorance and irrational fear, says Chestney, who hopes findings of the fish commission will help to change public perceptions.

People say rattlesnakes don’t get along with them. Well, yeah, they do,” he said. “It’s people who don’t get along with rattlesnakes.”

As a “species of immediate concern” in Pennsylvania, rattlesnakes have some protection. It is illegal to kill females, and mature males over 42 inches can be hunted, but only with a permit. Poaching is a problem, but the biggest threat to rattlesnakes is suburban sprawl, coal mining, Marcellus shale hydro-​fracturing, and other kinds of development that rob snakes of their forested habitat.

The big contiguous woods they like are disappearing or have become fragmented,” Chestney said. “That’s led to the demise of rattlesnakes in a lot of areas.”

Using old maps of ancestral dens as a starting point, Chestney and teams of volunteers have found that snakes still exist in 53 of Pennsylvania’s 67 counties, including Fayette, Somerset and Bedford, but not in their historical abundance.

Numbers is the big question,” says Chris Urban, the fish commission’s natural diversity chief, “and they’re not as stable as we thought.”

Central Pennsylvania’s big woods have the greatest density of rattlesnakes, though wildlife biologists aren’t sure for how long, because the same region is at the heart of the gas-​drilling boom.

Penn State University wildlife biologist Gian Rocco is monitoring the fate of rattlesnakes on 20,000 acres of forestland that the Commonwealth has leased to hydro-​frackers, by tracking 46 pregnant females and two young males surgically implanted with radio transmitters.

We’ve entered the Marcellus area and scientists are getting fidgety,” he said. “With any kind of energy development there is always collateral damage.”

Some edge deforestation could open up new foraging and basking opportunities for snakes, but any benefits would have to be weighed against impacts, such as gas pipeline and road construction, he said.

What’s critical is protecting their wintertime dens, and Rocco is monitoring where the snakes hibernate.

Mating occurs in summer when all but gravid females have come down from the mountains. Following the same paths they established as juveniles, males can range up to six miles to breed outside their own gene pool, though females stick a little closer to home. They mate in highly combative rituals with many different partners.

Two males who find a willing female will challenge each other by rising up and trying to look bigger and then engaging in a wrestling match,” said Urban. “They’ll wrap around each other’s necks and sway back and forth, and try to pin each other until the stronger male wins. The loser will slink away and the victor gets the female.”

Snakes journey back to their dens when nights turn cool in August. Their homing instinct is so strong that if they are removed from their range, they will become disoriented, sometimes with fatal consequences, said Urban.

They’ll frantically tongue-​flick and otherwise struggle out of desperation to find what’s familiar. Some will exhaust themselves to the point of death. Others will shut down and starve.” A young snake may find a new colony and adapt, Urban said. “But older snakes typically don’t.”

Impregnated females — who may be 10 years old before they have their first clutch — store sperm all winter and fertilize their eggs in spring. They give birth in August or September, delivering just seven to nine live offspring, and stay with them for a couple of weeks. “A lot of neonates get picked off by raccoons, raptors and other predators,” Chestney says. “Out of an entire clutch, only one young snake may survive.”

Chestney relies on GPS to locate familiar dens and uses his snake tongs for balance as he picks his way up the mountain. “This isn’t a job for sissies,” he said.

When he finds a snake — a three-​foot long golden-​yellow specimen — he moves quickly to capture it with tongs. The snake protests with a loud castanet-​like rattling of its tail as Chestney and an assistant force it, head-​first, into a ventilated plastic tube for safe handling.

Only its back end is exposed, and Chestney counts the subcaudal scales between the snake’s anal vent and rattle to determine she’s a female, and then palpates her to find that she is gravid. Working quickly, he inserts a sterilized needle above the rattle to draw blood, and then programs a micro-​chip the size of a grain of rice with the snake’s vital statistics, and gently implants it under her ribcage. “We don’t want to puncture one of the embryos she’s carrying,” said Chestney, whose final task is to measure the snake before releasing her to the rock where she was found.

Blood samples will help scientists determine the level of relatedness among snake populations around the state. Isolation and subsequent inbreeding are a concern in areas such as the South Mountain near Carlisle, where the population has dropped by 70 percent, the result of highway construction and sprawl.

Not all impacts on snakes are manmade. Tree growth in some forests is now shading gestation sites, where snakes once had sunlight for basking, Urban said. “We plan to prioritize areas where canopy can be opened up to help reproductive colonies.”

Constraining human impacts is a greater challenge, especially with the conservation status snakes currently have in Pennsylvania. The fish commission study could determine that they fit criteria for “threatened,” which would put Pennsylvania on par with neighboring states, though such a listing would probably be opposed by both developers and sportsmen, Urban said.

About 750 permits were issued last year, but fewer snakes were harvested, Urban said. “Some hunters kill snakes for their skin or meat, and a small percentage want to keep a live snake, but the majority of hunters these days just want to take photos.”

Even rattlesnake roundups — group hunts held in some rural communities — are tamer than they once were, and sacking contests were banned in the 1980s, he said.

Mustering widespread tolerance of snakes is a tougher sell. “Snakes aren’t what we call charismatic mega-​fauna,” Urban said. “People see them as ominous, and it’s true they’re an animal that can hurt you. But they’re really only dangerous if you harass or provoke them. They’re not going to come after you.”

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