Why did the rattlesnake cross the road? It didn't, and that's a problem, say conservationists.

New DNA analyses of rattlesnakes in New York State finds that even minor roadways deter snakes from crossing the road to breed. Populations are becoming isolated from each other by roadways, which may threaten their future.

"We worry for the health of these populations because connectivity is so key to responding to environmental pressures and avoiding inbreeding," said Rulon Clark of San Diego State University, who led the study published in Conservation Biology. The reduced genetic diversity that results from inbreeding makes populations less resistant to diseases or other disturbances.

Groups of up to dozens of rattlesnakes hibernate together in common dens, which serve as a home base. Come spring, they leave to hunt, and males strike out for neighboring dens to mate with females before returning to their home dens for winter.

The males' visits to nearby dens provide the genetic mixing necessary to keep a population from becoming inbred.

Clark and colleagues wanted to test whether roads were affecting the males' mating journeys. They collected blood samples from timber rattlesnakes in 19 different dens in different regions of New York State, including dens separated from each other by roads and others with uninterrupted forest between them.
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