Biologists are puzzled by the mysterious deaths of 104 endangered mountain yellow-legged frogs in breeding tanks at the Fresno Chaffee Zoo.
There are now only two frogs left at the zoo, one of three zoos participating in a wildlife breeding program to reintroduce frogs rescued after the 250-square-mile Angeles National Forest wildfire in Los Angeles two years ago.
Zoo director Scott Barton tells the Los Angeles Times that they haven't determined why the frogs died. He says the zoo may send the two remaining frogs elsewhere to see if someone else will have better luck.
"We were thrown a curve ball with a species that was new to us," Barton was quoted as saying by the Times. "It's been a humbling experience."
Fewer than 200 mountain yellow-legged frogs are believed to exist in nine isolated wild populations, including a group in the San Gabriel Mountains' Devils Canyon that survived the devastating Station fire, the Times reported.
Zoos in Fresno, Los Angeles and San Diego are involved in the public-private effort to re-establish the yellow-legged frog population in Southern California.
For thousands of years, mountain yellow-legged frogs thrived in hundreds of streams cascading down the San Bernardino, San Gabriel and San Jacinto mountains. Since the 1960s, the species has been decimated by fires, mudslides, pesticides, fungal infections, loss of habitat and the appetites of nonnative trout, bullfrogs and crayfish.
U.S. Geological Survey ecologist Adam Backlin, a lead scientist in the recovery effort, told the Times that "saving the mountain yellow-legged frog from extinction is turning out to be more difficult than anyone anticipated."