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Turtles in Decline

ESF study shows that most turtles killed on roads are females

Monday, November 01, 2004
By Mark Weiner Staff writer, Syracuse Post-Standard

A pair of scientists studying reptiles in Central New York say they figured out why the turtle crossed the road, and the answer has important implications for the future of the species.

The simple answer: Turtles crossing roads are mostly females looking for a warm, dry place to nest during spring and summer.

The bad news: Those females become road kill at much higher rates than males, according to a new study by scientists at the State University College of Environmental Science and Forestry in Syracuse. Advertisement

The study found that up to 95 percent of the surviving population of snapping turtles near high-traffic roads in the Syracuse area are male. Painted turtles are up to 74 percent male near those roads.

It's a disturbing discovery at a time when nearly half of the 56 turtle species in the United States are imperiled, said James P. Gibbs, an associate professor of conservation biology at ESF and the study's co-author.

Fewer female turtles could mean fewer offspring to replenish the population of a species known for having a long life and slow reproductive cycle, Gibbs said.

Gibbs and co-author David Steen published their study in a recent issue of Conservation Biology, a scientific journal. Gibbs said it is among the first studies to document the effects of road kill on turtle populations.

"Turtles have declined, and the causes are not entirely clear," Gibbs said. "Some of the species have just disappeared. Obviously, one of the greatest obstacles for turtles is this web of roadways."

Two other recent studies, conducted independently in New Hampshire and Florida, found similar trends: Turtle populations are suffering a high degree of road kill, Gibbs said.

Painted and snapping turtles were selected for the local study because they are two of the most common turtles in New York. The study examined their population in 35 wetlands along high-traffic and low-traffic roads in Central New York.

"We thought we would start looking at these least vulnerable turtles first," Gibbs said. "But I am quite convinced that road mortality is a huge issue for some species that are so rare now, such as wood turtles."

The United States is one of the world's hot spots for turtle diversity, with about 56 of the 257 known species. About 25 of those species in the United States require conservation attention, Gibbs said.

In New York, eight of the state's 16 turtle species are found in the Syracuse area. They are the snapping turtle, musk turtle, spotted turtle, bog turtle, wood turtle, painted turtle, Blanding's turtle and spiny softshell.

Gibbs and Steen say their study may have revealed important issues for turtle conservation since turtles do not adapt well to the loss of sexually mature adults.

Turtles do not become sexually mature for 12 to 15 years. As a result, the loss of adults can take a greater toll on the long-term health of their population.

Gibbs said he believes many of the turtles died on roads as they looked for nesting sites near dawn and dusk, about the same hours as peak traffic during morning and evening commutes.

For the study, Gibbs and Steen captured 174 painted turtles and 56 snapping turtles in 17 wetlands in high-traffic areas and 18 wetlands in low-traffic areas in Central New York.

They found that males dominated the surviving population in areas with the highest road density.

Among painted turtles, 74 percent were male in high road-density areas, versus 54 percent in low road-density areas.

In the meantime, he said road and highway engineers can take some relatively inexpensive steps to solve the problem.

A simple solution is a low barrier made of one or two layers of pressure-treated lumber, Gibbs said. More expensive solutions include animal underpasses and culverts, but he said those are not necessary along most roads.

© 2004 The Post-Standard.

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