Slammed by heavy winds and bearing precious amphibian cargo, the helicopter heaved skyward from a remote mountain ranch on the Baja California Peninsula.
With an outbreak of the coronavirus threatening to shut down the border between the U.S. and Mexico, biologists on both sides agreed it was time to act after months of wary deliberations. “It’s a go,” they announced.
At daybreak on March 14, two ice chests filled with 1,000 fragile red-legged frog eggs were airlifted from Baja California’s Sierra San Pedro Martir range to a landing site where they were loaded onto a pickup truck and driven to the U.S. port of entry.
It was a pivotal moment for the first binational effort aimed at reviving a federally threatened amphibian in California. But biologists who had spent 20 years laying the groundwork for it worried that nasty weather, combined with unforeseen permitting snafus and tightening travel restrictions due to the COVID-19 pandemic, might cause it all to unravel at the last minute.
“All eyes were glued to the ice chests as they moved through the turnstiles from the custody of Mexican authorities to U.S. customs officials,” recalled Robert Fisher, a research biologist with the U.S. Geological Survey.
Minutes later, he sighed with relief, smiled and said, “We did it.”
By noon, half the eggs had been placed just beneath the surface of the water in a pond at the Santa Rosa Plateau Ecological Preserve in the Santa Ana Mountains. The rest were placed in a small lake in a secluded, privately owned ranch in northern San Diego County.
Now, the eggs are starting to hatch, scientists say. If they survive to adulthood, they could help California’s state amphibian and largest native frog west of the Mississippi River repopulate some of the waterways where it thrived for hundreds of thousands of years.
The 4-inch-long frog named for the reddish color on the underside of its legs is expected to fare well. The sites offer deep pools buzzing with insects to feed on and dense stands of cattails for cover. They are also free of predatory bullfrogs and fish, who find few easier targets than tadpoles and juvenile frogs.
In a reversal of traditional relations along the border, it is biologists in the U.S. who will be seeking scientific information from experts at the small, family-operated nonprofit, Conservacion de Fauna del Noroeste in Ensenada, Baja California, if the project is to succeed. The effort involves the U.S. Geological Survey, the U.S. Fish and Wildlife Service, the California Department of Fish and Wildlife, the San Diego Natural History Museum and The Nature Conservancy.
Most of the research on the transplanted frogs, known to scientists as Rana draytonii, has been conducted by conservation biologist Anny Peralta-Garcia, co-founder of Fauna, and her husband, Jorge H. Valdez-Villavicencio.
“Anny is my hero,” said Bradford Hollingsworth, curator of herpetology at the San Diego museum. “Without the passionate work of the scientists at Fauna, the idea of recovering this species in Southern California wouldn’t be possible.”
In a telephone interview, Peralta, said, “As soon as I knew the eggs were safely in the water in California, I sent a congratulatory note to my staff of three that said, ‘This shows how a handful of people can accomplish things of international importance.’ ”
“Now, I hear that the eggs are hatching,” she added with a laugh. “I can’t wait to go see my babies.”
There was a time when California red-legged frogs numbered in the millions and their lustful calls joined the natural sounds of spring in ponds and streams from Point Reyes south to Baja California.
The amphibian, who won fame in Mark Twain’s “The Celebrated Jumping Frog of Calaveras County,” was long ago decimated by hunters, destruction of habitat, pesticides, fungal disease and the appetites of bullfrogs and crayfish. Today, the few small colonies that remain are on an ecological knife edge.
The recovery project began 20 years ago when the nonprofit environmental group The Nature Conservancy launched a bullfrog eradication campaign at the 8,400-acre Santa Rosa Plateau to help the red-legged frogs survive. At the time, in 1999, the species numbered two bachelors and a lone females. More recently, the organization raised the funds to pay for the helicopter flight that transported the red-legged frog eggs to the site near the border.
Rewilding the West isn’t easy. “Over the years, we’ve assembled safe habitat for these frogs and reinforced them with new ponds to serve as a refuge during droughts,” said Susan North, a project manager at The Nature Conservancy.
In 2002, the U.S. Fish and Wildlife Service identified core recovery areas on suitable public and private lands, including the plateau and the ranch in San Diego County, about 30 miles east of Oceanside.
In 2014, DNA research conducted by USGS found a close genetic match between extirpated red-legged frog populations south of Los Angeles County and colonies in Baja California.
Four years later, Fauna, with assistance from biologists at the San Diego Natural History Museum, built breeding ponds in red-legged frog habitat, which produced the masses of eggs that were transplanted in March.
Additional transplants are possible, officials said, and the populations they establish may be used to revive frogs in other locations in both the U.S. and Mexico where they have not been seen in as long as anyone can remember.
In a previous international effort to an save an imperiled species, critically endangered black-footed ferrets from captive breeding programs in the U.S. were reintroduced into the wilds of Mexico’s Chihuahuan Desert.
Critically endangered California condors from captive breeding facilities in California now soar over the Sierra San Pedro Martir range where Peralta’s team has been studying red-legged frogs in collaboration with scientists, including Hollingsworth.
“We looked up one day,” Hollingsworth recalled, “and noticed reintroduced California condors riding the thermals over a colony of red-legged frogs.
‘‘I couldn’t help but wonder: Wouldn’t it be a beautiful reciprocation, if we could send some of these frogs to places in California that they once shared with condors?”