Roadkill survey finds many amphibians

Death by car could be a major contributor to the decline of many amphibian species, according to the first comprehensive survey of roadkill, Purdue University researchers said this week.

The biologists found animals from more than 65 species killed along 11 miles of road in suburban Tippecanoe County outside West Lafayette, Ind. Nearly 95 percent of the dead were frogs and other amphibians, and three-quarters of the deaths occurred along a one-mile stretch of Lindberg Road that crosses a wetland known as Celery Bog.

Over the 17-month study, biologists Andrew DeWoody and Dave Glista collected 10,500 identifiable dead animals, they reported online in the journal Herpetological Conservation and Biology.

But they estimated that there were actually five times as many. The majority could not be identified because they were squashed beyond recognition, moldy and degraded or partially eaten by predators. They suspect many injured animals also left the roadway.

Previous studies of roadkill have focused primarily on mammals, which were a distinct minority in the new study. They found only four white-tailed deer, 43 raccoons and 79 opossums.

“We think of deer as being one of the animals more commonly killed on the road, but they actually make up a tiny percentage of the total,” said Glista, who now works as a biologist for the Indiana Department of Transportation.

The dead included 142 eastern tiger salamanders, which DeWoody found troubling.

“The absolute number might not look that large, but most of these individuals were mature, up to 10 years old. Many of them … were females bearing eggs on an annual trip to breeding ground where they often lay 500 to 1,000 eggs,” he said. “This could make a big difference for the population.”

They also found 74 dead northern leopard frogs, a species that is endangered in the region.

Glista said the ideal solution is to not build roads through wetlands and similar biologically rich areas. Alternatively, it should be mandatory to provide underpasses or other mechanisms for wildlife to cross the road safely.

He also noted that he had several close encounters with motorists while collecting the roadkill, even though he exercised extreme caution.

“I don’t want to become one of my own data points,” he said.