Species and Sprawl: A Road Runs Through It

Species and Sprawl: Wood Turtles

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While roads affect many species, this geometry can be especially devastating for some reptiles, which bank on the high survival rate of adults, rather than juveniles, to maintain their populations. Unlike the super-fecund hare, female wood turtles lay just a single clutch of about 10 eggs a year. Only a small percentage of the eggs hatch, and only a fraction of the hatchlings endure the dangers of raccoons and tractors and tarmac to reach adulthood at age 17. These survival odds, plus the fact that turtles have an impressive number of potential breeding years (some can live over a century) mean that adult turtle loss can seriously affect a species. “One study predicted that if two turtles were lost from a population annually,” says Jones, “the whole population would be lost in less than a hundred years.”

To compound the problem, Jones has learned that females ramble much greater distances from the river than do male turtles—sometimes 500 m to either side. Females, then, are more likely to encounter a road, which suggests that they are dying at a much faster rate than males. “Which is terrible,” says Jones. “You could keep a population around with fewer males for much longer than you could with fewer females.”

Unfortunately, human pressures—and fancies—take their toll on turtles in ways other than vehicular, namely via the pet trade. Wood turtles are particularly noted for their personality (In 1952, landmark herpetologist Archie Carr wrote in his Handbook of Turtles: “For all who have kept them are agreed that the wood turtle makes a better pet than any other [turtle] species.”). Today, however, capturing wild turtles as pets is illegal throughout the country.

Still, “poaching of turtles for the pet trade and collection of animals by recreationists continues to remove wood turtles from the wild,” says Sievert. “This can decimate local populations.” The effect on the population is exactly the same as if the turtle were killed on a highway.

What’s Around the Bend?

“Many people are convinced that the ideal situation is to have their home out in the woods,” says Sievert. “But if wildlife had a vote, they’d choose for humans to stay concentrated in urban centers rather than spreading ourselves out in a sprawling suburban environment.”

Sievert suggests that one long-term solution for the reduction of sprawl and its impact on wildlife would be for human population growth to reach zero. In the meantime, wise planning that incorporates the needs of wildlife—such as state-driven land purchasing, conservation easements, mitigation measures like road underpasses for turtle travel, or limiting development—could go a long way in reducing animal mortality and increasing population viability for threatened species in the United States.

Jones adds that the fate of wood turtles is representative of the fate of many creatures in wetland habitats, which are under particular attack by sprawl. “This species was clearly meant to be present throughout New England,” he says. “That was the case for probably the last six or eight thousand years. They have the right to go on existing here.”