Why did the turtle cross the road?

From Missoula, Mont., at the annual meeting of the Society for Conservation Biology

Turtles that try to outrace a car instead of a hare do not end well, but analyzing turtle mishaps is giving biologists new information about the animals’ habitats.

One of the first studies to monitor the number and gender of turtle traffic fatalities suggests that freshwater turtles move around on land more than expected, says Suzanne Fowle, now of the Massachusetts Division of Fisheries and Wildlife in Belchertown.

Just preserving wetlands is not enough to protect the animals, Fowle argues. The species she studied, Chrysemys picta bellii, or the painted turtle, crawl around drier land too and need safe passage to these areas.

Fowle started surveying dead turtles when officials proposed widening U.S. Route 93 where it cuts across Salish and Kootenai tribal land in western Montana. Local residents feared a wider road would lead to higher turtle fatalities.

To quantify the danger, Fowle and her colleagues at the University of Montana in Missoula patrolled 7 miles of route 93. Anecdotal reports were not exaggerations; between May and September 1995, researchers found 205 road-killed turtles.

The survey also “dispelled the myth that it’s mostly adult females that move around,” Fowle says. Forty-three percent of her collection was of adult males, and 26 percent was of adult females. The rest of the turtles were too damaged to reveal their gender, but Fowle could tell this portion included youngsters. “Everybody’s moving, all the time,” she says.

Fowle also found fewer turtles in wetlands closer to the road, compared with areas farther away, supporting the claim that the highway is reducing the turtle population. She says that current work on three eastern turtle species is finding similar high mobility.

Building turtle underpasses can help, but these structures need testing, Fowle cautions. Underpasses designed for desert tortoises have guided the animals out of harm’s way, but desert species naturally burrow. She’s not sure how other turtles would react. A better solution, Fowle observes, would be to avoid fragmenting an animal’s habitat to begin with.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.