Why Rattlesnakes Are Bold Road Crossers

So the seemingly simple question of why a snake crosses the road is not trivial at all. A snake that won't cross a narrow ribbon of concrete may have less of a chance to reproduce and survive than one that is willing to make a mad dash. And Andrews is finding plenty of snakes that won't go near the concrete.

For her research, Andrews uses snakes that have been captured in the sprawling wilderness that surrounds the lab. The area is rich with many species of snakes, some of which can be deadly, so she goes about her task with due caution.

The snakes are taken to the section of road, which is closed to vehicles, and slipped from a bag to beneath an inverted black plastic pot like those used by gardeners. The pot is hooked to a pulley atop a long stick. Andrews then retreats to the nearby woods and waits for the snake to settle down.

At this point, the snake has not seen the area, and when she yanks on a rope the pot is suddenly lifted. The snake can't see her, so as far as the snake is concerned, it's all alone in the woods, near a stretch of road.

With pencil in hand, Andrews records the actions of the snakes, some of which simply dart across the road. One common southern species, called a racer, can make it across the road in about 30 seconds, she says.

"You have a lot of snakes that will venture out onto the road, and they're kinda like, 'Whoa, I don't want any of this,' and they will turn around and exit," she says.

And some others, she adds, won't go near the road. Instead they beat a hasty retreat toward the woods.

The behavior varies greatly among species, she says. Rattlesnakes, for instance, don't seem to mind crossing the road and they take their sweet time about it. Maybe, she suggests, that's because a rattler has the ability to protect itself from predators and feels less vulnerable.

The racer doesn't seem to have any problems with the road, but Andrews is also studying snakes she encounters in the wild, and she has noticed a different behavior if the snake senses the presence of a vehicle.

"It freezes in the face of an oncoming car," she says, and that leads to an increase in road kills.

Rattlers may feel more secure as they meander across the roadway, but they rank among the leaders in road kills. One might suspect, given the rattler's nasty image, that many of those kills are not accidental.

Andrews sounds like she's having far too much fun with the project, given the fact that she has been fascinated with snakes all her life, but Gibbons thinks she's onto something.

"I think the research can be very significant in getting to the basic questions that have not been asked by herpetologists about why a snake, or any other animal, crosses a road in the first place."

Apparently it's a lot more complicated than just wanting to see what's on the other side.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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