Trekking into SoCal mountains to return very rare yellow-legged frogs to their home

The Los Angeles Zoo has released about 170 endangered frogs to their native habitat in the San Gabriel Mountains as part of ongoing conservation efforts for the species.

The release of the southern mountain yellow-legged frogs on Aug. 29 and 30 capped a trademark breeding process at the zoo, where the eggs of the rare amphibian are pampered and hatched.

The frog get their names in part from their habitat — where they thrived for centuries before populations declined to a handful of locations — in the perennial streams of the San Gabriel, San Jacinto and San Bernardino mountain ranges of Southern California. The name also derives from the yellow or light-orange coloration of their bellies, back legs and occasionally front legs.

The release of the frogs, known scientifically as Rana muscosa, was done in collaboration with the U.S. Geological Survey.

“This release is momentous for the L.A. Zoo as it marks another key milestone for our southern mountain yellow-legged frog breeding program,” Ian Recchio, the zoo’s curator of reptiles and amphibians, said in a statement. “We hope Angelenos will see this effort in their own backyard and think about actions they can take to help conserve wildlife.”

The species has been officially classified as endangered by the International Union for Conservation of Nature. Organized conservation efforts began in 2006 and have resulted in periodic re-introductions of frogs raised in captivity since then. The release is part of a long-term project to create 25 populations of a few hundred to a thousand frogs each.

The breeding in captivity starts with eggs hatched in a special amphibian breeding room at the L.A. Zoo. The room is temperature-controlled and has life support equipment on hand to create optimal living conditions for the frogs.

The tadpoles are later raised to adulthood at facilities at the Santa Ana Zoo in Orange County and the Aquarium of the Pacific in Long Beach. About 30 of the recently released frogs were not raised from birth, but instead rescued during the 2020 Bobcat fire and cared for by staff at the Aquarium of the Pacific.

Southern mountain yellow-legged frogs measure from 1.5 to 3.25 inches long. As adults, the frogs are typically brown and yellow, though some develop gray, red or greenish-brown hues. The animals are on display from May through November as part of the L.A. Zoo’s reptile, amphibian and invertebrate exhibit.

Times staff writer Louis Sahagún contributed to this report.