'On edge' of extinction

Press-Democrat 3/12/07

By Bob Norberg

Turtles have been on earth for 230 million years and survived three mass extinctions, including the one that wiped out the dinosaurs. Now, Sonoma State University students are trying to help the western pond turtle survive urbanization, the most dire menace yet.

"In the last 30 years, turtles have taken a big hit, and it is clear that it has been caused by man, whether it is habitat destruction or predation - turtles taste good," said Nick Geist, a SSU assistant professor of biology. "Turtles are on the edge."

The western pond turtle and the desert tortoise are the only native California turtles, and there are so few pond turtles left that they are a species of special concern, necessitating a special permit to handle them.

The pond turtle ranges from Mexico to the Canadian border in a narrow strip along the coast, lives to be 60 years old and its shell gets as large as 12 inches in diameter.

Ninety percent of its habitat has been lost, however, by man turning marshes into housing subdivisions and creeks into cement-lined flood-control channels, Geist said.

"In Southern California, they have been wiped out," Geist said. "In San Diego, Los Angeles, Santa Barbara, where the turtles were commonplace, they are nowhere to be found."

"They used to be all over the Central Valley, and now they are extinct," said Kit Crump of Santa Rosa, a fisheries biologist with National Oceanic and Atmospheric Administration, who estimated the population at one time was 3.5million.

Baby turtles also are favorites of big-mouthed bass and bull frogs, both non-California natives; turtle eggs are favorites of skunks and raccoons; and the non-native Red-eared slider competes for territory.

The western pond turtle has seemed to adapt well to man-made locations, such as the SSU ponds, Ledson Marsh at Annadel State Park and agriculture reservoirs.

At SSU on Friday, students gathered at the university's two ponds, where two turtles were netted. They were studied to determine their type, sex and age, and over time students will try to get an indication of how many there are.

"One of the first aspects to look at is the population of turtles, how many, do we have young turtles, do we have old turtles, are they breeding," Geist said.

The female turtles will be fitted with radio transmitters to allow students to follow them to their nests, where their eggs will be gathered for incubation.

Geist has received $9,500 from SSU and the Sonoma County Fish and Wildlife Council to buy the transmitters and incubators.

Because the sex of the turtles is determined by the temperature of the eggs at hatching - cold temperatures it's male, hot it's female - the eggs will be incubated at different temperatures to find the critical temperature, Geist said.

Once that is determined, scientists can manipulate the population to produce more females, for example, if a pond has too many males.

Graduate student Becki Gordon of Petaluma is heading the study as part for her master's thesis.

"I've always been interested in reptiles, especially turtles," Gordon said. "They're kind of archaic."