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Wednesday, 01 August 2007 00:00

Slithery study: WCU professor studies to see just how sensitive timber rattlesnakes are to human development

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By Michael Beadle

Ron Davis is tracking a very special timber rattlesnake along a road at Balsam Mountain Preserve in Jackson County.

In late July, the snake was released back into its habitat after undergoing surgery to have a transmitter placed inside its body. That way, Davis, a natural resources management professor at Western Carolina University, can track the snake with a radio transmitter to learn more about its behavior, habitat and where it will den this fall. This, in turn, should reveal important clues about how timber rattlers survive despite increasing human development carving roads and homes through the very places snakes have long held as a refuge.

Listed as a species of “special concern” in North Carolina, timber rattlers are not yet endangered, but their populations are declining dramatically in Western North Carolina due to poaching, wonton killing, and increased human development - particularly road building.

Timber rattlers - and reptiles in general - tend to be sensitive to environmental changes and have a slow reproductive cycle, so their populations can take years to bounce back if they lose their natural habitat or their den gets disrupted.

Jennifer Slagle, a WCU rising senior from Shelby, created a computer model indicating where timber rattlers might be found based on previous studies detailing temperature range, elevation, soil composition and access to shade and rocks. Using Slagle’s model, Davis and his students hope to find timber rattlers, implant transmitters in them and then release them to study them in their habitat. Slagle, a double major in political science and natural resources management, plans to graduate this December. Before she leaves Western, however, she’ll review her computer model with Davis to see if it proved accurate for finding timber rattlers - especially when considering other factors like the effects of human development.

“I’m hoping to help him a little more with the research,” she said.

Despite having a dangerous reputation, rattlesnakes tend to keep away from humans. They are defensive animals when threatened, but they are not aggressive. Given the chance, they’ll move away, Davis explained. In the case of the timber rattler, it likes to keep close to rocks and vegetation that offer just the right mix of protection and temperature regulation. If it’s too hot, snakes can die, so you probably won’t see them fully exposed on a rock sunning themselves. They also keep out of sight to avoid becoming another animal’s prey.

One problem with human-snake encounters is relocation. Moving a timber rattler out of its home range is a death sentence.

“It’s like dropping us in the middle of the jungle; we don’t know where we are,” Davis said.

Snakes become disoriented if they’re taken out of their home range because they depend on scent trails. Losing the scent creates stress, which can kill them. Research has shown that moving a timber rattler a short distance - about 100 yards - can deter the animal from returning to the point of capture and still enables it to find its home range.

The purpose of Davis’ research at Balsam Mountain Preserve is to track snakes to their den sites - partly to learn more about snake behavior but also to protect these habitats from prospective home builders who surely wouldn’t want to erect a house in the middle of a snake breeding ground. Likewise, taking out a den site would be catastrophic for the snake population.

“If you’ve destroyed the den site, then you’ve destroyed the whole population,” Davis said.

In Western North Carolina, timber rattlers emerge from their dens around April when the ground is warm enough and then they’ll seek shelter in dens by October as cooler temperatures prevail.

Timber rattlers can grow up to six feet long, but the ones Davis has seen tend to be about three or four feet long - the males generally bigger than the females. When snake populations were larger, it’s likely there were also more large snakes, Davis explained. Timber rattlesnakes can live up to 20 years but don’t reproduce until they’re eight or nine years old, and even then there’s a minimum of two to four years between breeding. They breed in the fall, but a delayed fertilization means gestation won’t begin until spring, and then they’ll give birth to eight to 10 baby snakes in late summer.

At Balsam Mountain Preserve, Davis uses a radio antenna and tracking receiver to listen for a series of beeps sent out by the transmitter implanted in the snake. When the beeps grow stronger, Davis knows the snake is close. The transmitter, which is about the size of a AAA battery, was implanted under the snake’s ribcage by Asheville wildlife veterinarian Dr. Lee Bolt in mid-July. But even with the help of GPS and other high-tech gadgetry, it can be difficult to spot a camouflaged snake that doesn’t want to be disturbed.

“You can end up on top of the animal before you realize it,” Davis says.

After a few minutes of searching, he finds exactly what he’s looking for - about a hundred feet from where he spotted the rattler the previous day. Even though he steps a few feet from the snake, it doesn’t so much as flick its tongue or emerge out of its coil.

Named after the sound of their rattles, which they add to with each successive molt or skin-shedding, timber rattlers use this feature as a defense mechanism. In fact, other snakes demonstrate the same tail-wagging behavior even if they don’t have rattles. The rattling sound isn’t like a baby’s rattle as we are taught to imagine. Instead, it sounds more like a buzz, Davis explained.

Counting rattles on a rattlesnake isn’t a reliable measure of knowing its age, Davis added, since some rattles can fall off the snake the older it gets.

The timber rattlesnake, or Crotalus horridus, lives throughout the Southeast and as far north as Maine. Not to be confused with its much larger cousin, the eastern diamondback, the timber rattlesnake produces venom for feeding. The venom is actually a digestive enzyme. A single bite is intended to kill its prey, which includes small rabbits, rodents and birds. Because the venom is precious to the snake and biologically costly to produce, a timber rattler won’t always waste its venom in a defensive bite - on a human, for example - so these types of bites tend to be “dry” or venomless.

Still, Davis cautions, it’s important to stay alert and be very careful around a timber rattlesnake.

Davis, who grew up in Indiana, did his doctoral work at the University of Illinois before taking his position at Western Carolina University last August. Part of what attracted him to the region was its biodiversity.

“I really wanted to be here if I could,” he said. “I always wanted to do exactly what I’m doing now.”

Exploring the woods, ponds and farms of west central Indiana as a kid, he found a natural curiosity for all sorts of animals.

“I was always fascinated with wildlife,” Davis said. “I was always trying to catch things.”

Once when he was about 10 years old, he captured a baby blacksnake and brought it back to his house, where it promptly got loose from its shoebox.

“I never did see the snake again,” Davis recalled. “My mother still lives in that house, but I don’t know if she ever knew about the snake.”

These days, his field research is providing Balsam Mountain Preserve and other sites in Haywood and Jackson counties with a chance to learn more about wildlife species and to find ways that humans and snakes can live together peacefully.

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