It seemed like an odd idea at the time, building tunnels under a busy road to help California tiger salamanders travel safely from their hillside homes to a nearby pond where the endangered species can breed.
The plan, however, appears to have worked, according to biologists who are studying the tunnels, built two years ago under Stony Point Road near Cotati.
"I haven't analyzed all the data. Everything is preliminary, but just a broad general conclusion is these crossing tunnels are working. They are functional, and salamanders are using them," said Tracy Bain, a graduate student at Sonoma State University.
The San Francisco resident is writing her thesis on the effectiveness of the tunnels for a masters degree in conservation biology.
"There are lots of things that fragment habitat of migrating animals," Bain said. "For these salamanders, who go from their upland habitat, where they are year-around, to the pond, the road is the problem."
The tunnels were constructed two years ago by Sonoma County, using a $150,000 grant from a Caltrans fund to offset environmental effects of roadwork.
It was an idea proposed four years ago by David Cook, a senior environmental specialist for the Sonoma County Water Agency who studies amphibians, such as frogs and salamanders.
California tiger salamanders are 8-inch amphibians with bright spots that live in gopher holes but come out during the first evening rains of winter, migrating as far as a half-mile to breed in ponds.
One such breeding area is near Cotati, where the tiger salamanders live in the uphill grasslands on one side of Stony Point Road. The breeding ponds, where they lay their eggs, is on the other side of the road.
"I was doing wildlife studies for a Water Agency proposed pipeline in the area and I found this major migration route that crosses Stony Point and a frequent mortality," Cook said.
The salamanders were listed as an endangered species in Sonoma County in 2003 by the U.S. Fish and Wildlife Service, becoming a lightning rod for criticism by developers and growth advocates, who complain the amphibians' protected status holds up projects.