AUDIE CORNISH, host:
From the search for answers to life, the universe and everything to a much more basic question of survival. Scientists in California, working with the San Diego Zoo, are taking extraordinary steps to save an endangered frog. The yellow-legged mountain frog used to be in nearly every range in Southern California. But after years of drought, fire, floods and a deadly fungus, only about 150 of those adult frogs live in the wild today.
Here's NPR's Carrie Kahn.
(Soundbite of footsteps)
CARRIE KAHN: Biologist Frank Santana walks on an icy-cold trail high in the San Jacinto Mountains, east of Los Angeles. Last summer, he put dozens of endangered yellow-legged tadpoles in a creek here. They've been in cages the whole time getting acclimated to the wild.
He's come back after the first winter snow, ready to set them free.
Mr. FRANK SANTANA (Research Technician, Institute for Conservation Research, San Diego Zoo): Careful crossing this wooden bridge. You don't want to fall in the creek.
KAHN: Santana had been raising the tadpoles since they were rescued from a nearly dried-up pond not far from the stream. Years of low rainfall and a fire in the region had all but destroyed the endangered frogs' natural habitat.
He's ready to let them go now. In chest-high waders, Santana steps into the frigid water and opens the lid on one of the cages.
Mr. SANTANA: All right, we got our first tadpole here, got him in the net. Got another tadpole here and they look really good. They're swimming around fine. They look nice and fat and healthy. It's pretty awesome that they all survived for three months.
We introduced them in late August, and they've been in the cages ever since. And we're really happy that they survived.
KAHN: Yellow-legged mountain frogs used to live all over the mountains of Southern California and in the Sierra Nevada range. But since the 1970s, nearly 90 percent of the population has been lost.
Geologist Rebecca Fenwick attributes that loss to several reasons, like fire and floods, which are prominent in Southern California. But she says it's also not as cold here as it used to be.
Dr. REBECCA FENWICK (Geologist): In the last 15 years, it's gotten warmer in the winters. It doesn't stay cold in the same way, so the storms don't build up and generate a large snowpack at this elevation.
KAHN: Without a good snowpack, there isn't enough water to last through the summer and the frogs - and especially the tadpoles - haven't been able to survive. Fenwick says this creek is at a high enough elevation so it won't completely dry out.
Habitat destruction is a problem not for just this species of frog. Worldwide, 30 percent of frogs are in danger of extinction.
Dr. BRIAN GRATWICKE (Biologist, Smithsonian Conservation Biology Institute): They're disappearing much faster than any other vertebrate that we know of.
Brian Gratwicke works at the Smithsonian Conservation Biology Institute in Washington, D.C., and is a leading amphibian expert. He says since 1980, more than 120 amphibian species have vanished from the planet. In that same time period, only five bird species have been lost and no mammals have gone extinct.
Gratwicke says thousands of people are dedicated to saving mammals and birds, but only a handful work to preserve amphibians.
Dr. GRATWICKE: I know that amphibians might not be as popular as other vertebrates, like birds and mammals. But they are, in my mind, a very important group of vertebrates.
KAHN: Gratwicke says that since frogs live in both the water and on land, they can be an early indicator for problems in either environment. He says in the U.S., there are species of frogs that now survive only in zoos.
(Soundbite of running water)
KAHN: Biologist Frank Santana has been working for years to make sure the yellow-legged mountain frogs' future will include life outside the San Diego Zoo, hopefully high in the San Jacinto Mountains of Southern California.
Mr. SANTANA: So we got the tadpole out of the cage, the last one. So I'm pretty excited that they're all alive and they look really good.
KAHN: He knows it's unlikely that all 36 tadpoles will grow up to be adults. But Santana is hopeful and says he's learned a lot about how to re-introduce these frogs back into the wild.
Carrie Kahn, NPR News.