THOUSAND OAKS, Calif. >> A discovery involving a rare California frog has researchers hopping for joy.

Nine egg masses from the California red-legged frog were discovered on March 14 in a creek in the Santa Monica Mountains, which stretch from Los Angeles westward along the Malibu coast into Ventura County.

The threatened species hasn’t been seen naturally in the mountains since the 1970s and the National Park Service has been trying to rebuild the population by transplanting eggs from a population in the nearby Simi Hills.

The discovery of new egg masses indicates that after four years of effort, the population is showing signs of sustaining itself without human help, although transplants will continue, the park service indicated.

“I was literally crying when the stream team showed me the photos of egg masses,” Katy Delaney, a National Park Service ecologist with Santa Monica Mountains National Recreation Area, said in a statement. “The years of work we’ve put in is showing amazing progress. There’s still plenty of work to be done, but this is a major moment for the project.”

Red-legged frogs famously appear in the Mark Twain story, “The Celebrated Jumping Frog of Calaveras County.”

At 2 to 5 inches long, they are the largest native frogs in the West and once were found throughout the state. However, habitat loss, pollution and the rise of nonnative species such as crayfish and predatory bullfrogs have vastly shrunk the population.

Efforts are underway to restore the species in other areas. Last year, thousands of tadpoles were released in Yosemite National Park, where the natural population vanished more than 40 years ago.

Thousands more tadpoles and adult frogs are being bred at the San Francisco Zoo & Gardens for release in the park.