CONSERVATION BIOLOGY (Arlington, Virginia) August 2004 Roads May Skew Turtle Sex Ratios - Painted and snapping turtles almost all male near major roads
Anyone who's seen a turtle cross the road knows that these slow-moving reptiles are no match for the cars whizzing past. But there has been little evidence that roads are a threat to turtle populations. Now new research suggests that cars are picking off the females: painted turtle populations are 73% male and snapping turtle populations are 95% male near roads in upstate New York.
"Our study indicates that females may be taking the brunt of the road kill," says James Gibbs, who presents this work with David Steen in the August 2004 Conservation Biology. Both researchers are at State University New York, Syracuse; Steen will be at the Joseph W. Jones Ecological Research Center in Georgia beginning in August.
The U.S. has about a fifth of the world's turtle species (about 56 out of 257) and nearly half of them are imperiled. Roads are a likely threat to turtles because the juveniles migrate to find new places to live, and the adults migrate to find mates and nest sites. However, linking roads to declining turtle populations has been difficult because much of the road expansion has been relatively recent and turtles can live for more than 40 years, which means that even disturbed populations could persist for decades.
Study co-author Dave Steen with a large female snapping turtle. Females are disproportionately impacted by roads.
Steen and Gibbs compared the sex ratios of painted and snapping turtle populations in 35 wetlands in areas with high and low road densities near Syracuse, New York. Most of the high road density study sites were near the New York State Thruway and Interstate 84, while the low road density study sites were in protected areas including Howland Island Wildlife Management Area and Three Rivers Wildlife Management Area.
The researchers found that "high road density" turtle populations had many more males than "low road density" populations: painted turtles were 73% vs. 54% male, respectively, and snapping turtles were 95% vs. 74% male, respectively. This suggests that more females are killed on roads, presumably during their spring-summer nesting migrations. Fewer female turtles could mean fewer baby turtles to replenish the populations.
Turtles can be protected from traffic near wetlands by installing culverts to help them cross roads and short fences to keep them from crossing roads. People can also help turtles by moving them off roads. "When you see a turtle crossing a road in the spring or summer, there's a good chance it is a female full of eggs, so don't hit it and don't take it home or relocate it miles away," says Gibbs. Instead, turtles should be put on the side of the road they were trying to reach.
CONTACT:
David Steen: 845-699-2547, DavidASteen@yahoo.com
James Gibbs: 315-470-6764, jpgibbs@syr.edu (NOTE: James Gibbs will be unavailable until August 5)
Roads May Skew Turtle Sex Ratios