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Reintroduced frogs are staying alive in the Santa Monica Mountains

One of a handful of juvenile California red-legged frogs who have survived their first year in the Santa Monica Mountains, the first of the species to live in the Santa Monica Mountains since the 1970s. Biologists hope the juveniles will survive into adulthood and will begin breeding in the spring of 2016. Courtesy of the National Park Service. National Park Service

A threatened species of frog has taken a hop towards recovery in the Santa Monica Mountains.

A handful of juvenile red-legged frogs have survived a year living in various locations along two of the mountain range’s streams.

“We go out there twice a week, and we see juveniles almost every time,” said Katy Delaney, a wildlife ecologist for the National Park Service. “It’s great. We didn’t know if that was going to happen, so it’s very exciting.”

The amphibians were transplanted as eggs last year as part of the first-ever attempt to reintroduce the species to the Santa Monicas after a decades-long absence.

Delaney and other scientists released hundreds of the hatched tadpoles into the waters last July.

It’s not possible to know how many of the frogs are still alive, because the frogs are active at night, and most monitoring is done in person during the day. The scientists involved in the study can only give estimates of “a handful.”

Delaney said studies have shown that typically one to five percent make it to adulthood in the wild. She said she believes at least 15 are still alive.

“We think there’s probably more than that, but we really don’t know. We don’t actually see more than that in any one visit,” she said.

She said that low numbers are not unexpected and that she’s encouraged by the persistence of the individuals she does see.

“We only see a handful anytime we go out there, but they’re in different places, different pools. They’re not always in the same place, and so we think that there are sort of a few spread across each of the translocation sites, which is really good news,” Delaney said.

Will they make it to mate?

Red-legged frogs are the largest native species of frog in the Western United States. The juvenile frogs still have about a year to grow before they attain adulthood and begin reproducing. Surviving adults could begin procreating early next year.

Many predators could further winnow down the frog population in the meantime. Raccoons, skunks, coyotes, foxes and even some birds may dine on the amphibians.

Delaney and her team have continued their reintroduction efforts. They released hundreds of additional tadpoles last week.

The eggs they used were collected from a variety of masses and source pools, thus increasing the chances of releasing progeny from a variety of parents.

“We’re trying to increase the genetic variability of what we’re taking as much as we possibly can, even though that source population is pretty genetically inbred due to its isolation for the last at least 50 or 60 years,” Delaney said.

Those tadpoles could face an even tougher childhood than their pioneer cousins, because juvenile and adult red-legged frogs are known to prey on the tadpoles of their own species.

“Juvenile red-legged frogs that are in the stream now — those could be predators of tadpoles and young frogs of this year,” Delaney said. “And if we’re lucky enough to get adults next year, they’ll be eating everything. They sort of eat whatever they can get their mouths around.”

Still, cannibalism aside , successfully reproducing adult red-legged frogs would be welcomed by Delaney.

In the meantime, she said she is heartened by the ongoing success of the remaining juveniles.

“It’s still exciting every time I see one, and I think, ‘Wow, you know, we put that there’" she said. "It’s very exciting still. I’m feeling good."