Rare frogs have returned to the San Gabriel Mountains


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

Juvenile, inch-long, Southern California mountain yellow-legged frogs were carried on foot to a pair of secluded spring-fed streams running through some of the wildest spots in Los Angeles County. No sidewalk. No campgrounds. No predatory trout. No trails. No fingerprints.

The foray was led by US Geological Survey biologists Adam Backlin and Elizabeth Gallegos, who for two decades have been assessing the ecological effects of summer crowds and heat waves, drought, wildfires and flooding caused by the climate in the mountains just north of Los Angeles.

A yellow-legged frog from the mountains of southern California. The species thrived for thousands of years in hundreds of year-round flowing streams in the San Gabriel, San Bernardino, and San Jacinto Mountains.

(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 on the move as the climate changes at a staggering rate. The most noticeable change was the disappearance of mountain streams and the effect this had on the yellow-legged frogs – their life’s work.

Like someone who saw their neighborhood fall into disrepair, Backlin said, “Many waterways have been overrun with recreational activities or just dried up. As a result, frog populations have also declined or disappeared.

The yellow-legged frog has thrived for thousands of years in hundreds of year-round cascading streams in the San Gabriel, San Bernardino, and San Jacinto Mountains. Today, according to federal biologists, about 200 yellow-legged frogs barely cling in isolated wild populations along a handful of hard-to-reach waterways.

The rapid disappearance of suitable riparian habitat compounds the terribly complex ecological and regulatory issues facing state and federal authorities charged with protecting the frog and other native species that will not have time to adapt or avoid extinction.

Biologists originally planned to release frogs into three streams on Thursday. One of them, however, evaporated in August.

Another drought summer bringing flooding and debris flows from fire-bared slopes could wipe out the few remaining places with the comforts needed to complete the life cycle of the rare – and unusually tough – amphibian that spends two years as a tadpole that prefers clear, calm, icy ponds shaded by alders, willows, and oaks.

US Geological Survey biologist Liz Gallegos, center, leads her teammates through the Angeles National Forest

US Geological Survey biologist Elizabeth Gallegos, center, leads her teammates as they sort containers of Southern California mountain yellow-legged frogs for release in a pair of secluded creeks in the forest Angeles National.

(Brian van der Brug/Los Angeles Times)

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

A mountain yellow-legged frog wriggles in a plastic container. In 2002, when it was listed under the federal endangered species law, there were fewer than 100 adult yellow-legged frogs left in southern California.

(Brian van der Brug/Los Angeles Times)

The good news: the amphibians released on Thursday effectively doubled the number of wild yellow-legged frogs. Whether they will spur future generations in the drought-stricken Angeles National Forest, overlooking the roar and bustle of 18 million people in the cities below, remains to be seen.

“Before, these frogs were almost everywhere,” Gallegos said. “One of our biggest challenges right now is just finding habitat that will still be there in a few years.”

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 would have been hard to imagine an amphibian less likely to face imminent extinction within the range, which is managed by the US Forest Service and includes the San Gabriel Mountains National Monument.

But since then, the frog named after the bright yellow that extends from the underside of its hind legs to its lower belly has been decimated by the appetites of non-native trout, bullfrogs and crayfish, as well as the extreme climate change. With skin as permeable as a sponge, the frog is also highly susceptible to a fungus related to globally endangered amphibians.

The San Gabriel Mountains inside the Angeles National Forest

In the mid-1960s, it would have been hard to imagine an amphibian less likely to face imminent extinction in the San Gabriel Range, which is managed by the US Forest Service.

(Brian van der Brug/Los Angeles Times)

In 2002, when the species was listed under the federal endangered species law, fewer than 100 adult yellow-legged frogs remained in southern California, giving 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 nation’s most ambitious and frustrating wildlife research projects in recent history.

In their natural habitat, frogs flock to streams gushing from melting snow in the spring. Males announce their availability for amphibian romance with a low-pitched underwater bark. In the dead of winter, yellow-legged frogs hide under a mud bank under a blanket of snow.

Early attempts at breeding frogs had limited success. That’s because the innermost details of their breeding behavior remained a mystery until Ian Recchio, the Los Angeles Zoo’s reptile curator, discovered how to turn a small building into a “frog house” that mimics the life cycle of the frog: winter hibernation, spring thaw. and the mating season.

Today, the zoo produces thousands of eggs and tadpoles each year, many of which are 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 computer scientist Dam Nguyen begin their three-mile trek to release Southern California’s yellow-legged mountain frogs in the Angeles National Forest.

(Brian van der Brug/Los Angeles Times)

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

With the abundance of new arrivals from the Los Angeles Zoo, the Aquarium of the Pacific and the Santa Ana Zoo have set up holding facilities equipped to raise tadpoles into froglets available for reintroduction projects.

On Thursday morning, staff helped load coolers containing 175 froglets from the aquarium and 25 from the Santa Ana Zoo into vehicles that transported them to the mountains.

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

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

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

Backlin’s response was reassuring. “The frogs are happy,” he says. “And I would be happy too if I came back there next year to find that the frogs and the streams are alive and well.

“But I really think,” he added, “we’re on a roll now.”


Los Angeles Times

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