Rare yellow-legged frogs are being returned to the drought-stricken San Gabriel Mountains

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On Thursday morning, six biologists carried backpack coolers filled with 200 federally endangered frogs and began trudging uphill through three miles of roadless wilderness on the northwestern flanks of the San Gabriel Mountains.

The two-inch-long juvenile Southern California yellow-legged frogs were carried on foot to some remote, spring-fed streams that run through some of the wildest places in Los Angeles County. No pavement. No campsites. No predatory trout. No trails. No footprints.

The search was led by biologists Adam Backlin and Elizabeth Gallegos of the U.S. Geological Survey, who for two decades have been assessing the ecological effects of summer crowds and climate-driven heatwaves, drought, wildfires and flooding in the mountains just north of Los Angeles.

A Southern California mountain cedar frog. The species thrived for thousands of years in hundreds of streams that flowed year-round through the mountains of San Gabriel, San Bernardino, and San Jacinto.

(Brian van der Brug / Los Angeles Times)

They can attest that in these mountains, the rippled slopes, lush canyons and the creatures that inhabit them are all in flux as the climate changes at an unnerving pace. The most notable change is the disappearance of mountain streams and the effect that has had on yellow-legged frogs – their life’s work.

Like someone who has seen his neighborhood fall into disrepair, Backlin said, “Many streams have been taken over by recreational activities or have simply dried up. As a result, frog populations have declined or disappeared.”

The yellow-legged frog thrived for thousands of years in hundreds of streams that flowed year-round through the mountains of San Gabriel, San Bernardino and San Jacinto. Today, federal biologists say, about 200 yellow-legged frogs barely live in isolated wild populations along a handful of hard-to-reach streams.

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The rapid disappearance of suitable riparian habitats exacerbates the agonizingly complex ecological and regulatory problems facing state and federal wildlife authorities charged with protecting the frog and other native species that will not have time to adapt or avoid extinction.

The biologists originally planned to release frogs into three streams on Thursday. However, one of them evaporated in August.

Another summer of drought culminating in flooding and debris flows from fire-stripped slopes could wipe out the few places left with the creature comforts needed to complete the life cycle of the rare — and unusually finicky — amphibian, which spends two years as a tadpole. prefers clear, calm and icy pools shaded by alder, willow and oak.

US Geological Survey biologist Liz Gallegos, center, leads teammates in Angeles National Forest

US Geological Survey biologist Elizabeth Gallegos, center, leads teammates as they sort containers of Southern California yellow-legged frogs in preparation for their release into some remote creeks in Angeles National Forest.

(Brian van der Brug / Los Angeles Times)

A yellow-legged mountain frog wriggles in a plastic container.

A yellow-legged mountain frog wriggles in a plastic container. In 2002, when it was listed under the federal Endangered Species Act, fewer than 100 adult yellow-legged frogs remained in Southern California.

(Brian van der Brug / Los Angeles Times)

The good news: The amphibians released Thursday have effectively doubled the numbers of wild yellow-legged frogs. Whether they spur future generations into the drought-stricken Angeles National Forest overlooking the clatter and commotion of 18 million people in the cities below remains to be seen.

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“Once upon a time, these frogs were almost everywhere,” Gallegos said. “One of our biggest problems right now is finding a habitat that will still be there a few years from now.”

The release was part of a long-term project to create 25 populations of a few hundred to a thousand frogs each.

In the mid-1960s, it was hard to imagine an amphibian being less likely to face extinction in the area, which is administered by the US Forest Service and includes the San Gabriel Mountains National Monument.

But since then, the frog has been named for the bright yellow that stretches from the undersides of its hind legs to its abdomen, decimated by the appetites of non-native trout, bullfrogs and crayfish, as well as shifting extreme weather events. With skin as permeable as a sponge, the frog is also highly susceptible to a fungus associated with amphibians that are disappearing all over the world.

The San Gabriel Mountains in the Angeles National Forest

In the mid-1960s, it was hard to imagine an amphibian being less likely to face extinction in the San Gabriel area, which is administered by the US Forest Service.

(Brian van der Brug / Los Angeles Times)

In 2002, when the species was listed under the federal Endangered Species Act, fewer than 100 adult yellow-legged frogs remained in Southern California, earning it the distinction of being one of the rarest vertebrates on Earth.

A subsequent effort to develop a successful captive breeding and reintroduction program became the focus of one of the country’s most ambitious and frustrating wildlife research projects in recent memory.

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In their native habitat, the frogs migrate to streams flowing from the melting spring snow. Males announce their availability for amphibian novel with a low underwater bark. In the dead of winter, yellow-legged frogs crouch under a mudbank under a blanket of snow.

Early attempts to breed the frogs had limited success. That’s because the most intimate details of their reproductive behavior remained a mystery until Ian Recchio, the reptile curator at the Los Angeles Zoo, discovered how to transform a small building into a “froghouse” that mimics the frog’s life cycle from hibernation. , spring thaw and mating season.

Now the zoo produces thousands of eggs and tadpoles every year, many of them descendants of frogs rescued from wildfires, including the devastating 2020 Bobcat fire, which charred 115,796 acres in the central San Gabriel Mountains.

Hikers along a creek in the Angeles National Forest

US Geological Survey biologist Adam Backlin, left, and IT specialist Dam Nguyen begin their three-mile trek to release the Southern California yellow-legged frogs into the Angeles National Forest.

(Brian van der Brug / Los Angeles Times)

The joint recovery effort includes the Los Angeles Zoo; the San Diego Institute for Conservation Research; the Henry Doorly Zoo and Aquarium in Omaha; the U.S. Forest Service; the US Fish and Wildlife Service; the US Geological Survey; and the California Department of Fish and Wildlife.

With the LA Zoo’s plethora of newcomers, the Aquarium of the Pacific and the Santa Ana Zoo installed rescue facilities equipped to raise tadpoles into frogs available for reintroduction projects.

On Thursday morning, staff helped load ice chests containing 175 frogs from the aquarium and 25 from the Santa Ana Zoo into vehicles that would transport them to the mountains.

But saying goodbye was not easy. A few days earlier, Brett Long, the aquarium’s conservator of mammals and birds, was only joking when he folded his hands in prayer and said with a smile, “We wish these little frogs all the frog-style health and prosperity in the world as they go to their new home.”

Amber Soto, who oversees the yellow-legged frogs at the Santa Ana Zoo, said: “This is a species in our own backyard that desperately needs our help. So it’s really exciting to lend a hand.”

At the same time, she added, “My big Friday morning question will be this: are our frogs all right up there?”

Backlin’s response was reassuring. “The frogs are happy,” he said. “And I’ll be glad, too, when I walk back up next year to find that both the frogs and the streams are alive and well.

“But I really think,” he added, “we’re on the right track now.”

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