Mountain Yellow-legged Frog Gets a Jump Start in Survival

A mountain yellow-legged frog with just eyes and mouth sticking out of the water and vegetation

Adult mountain yellow-legged frog peers out of its cryptic habitat within the Dark Canyon Campground closure area. Photo: A. Bower

The San Bernardino National Forest (SBNF), and partners are helping the mountain yellow-legged frog battle back from near extinction, by providing a scientific based recovery process including a captive breeding program and the identification and rehabilitation of suitable habitat in the wild.

The Mountain Yellow Frog (Rana mucosa), a California native, has a long journey ahead towards recovery from the very brink of extinction.

Thanks to a partnership between several agencies including the SBNF, US Geological Survey, US Fish & Wildlife Service, California Department of Fish and Wildlife, California Department of Transportation, the Los Angeles Zoo, and the San Diego Zoo, a captive breeding program, coupled with relocation to historic locations where the frog once thrived, has brought new hope for recovery of the species.


Raising Tadpoles in Captivity

Scientists at the San Diego Zoo Institute for Conservation Research (Institute) have been working to develop captive breeding techniques for the MYLF since 2007. They succeeded in producing more than two thousand tadpoles in 2016! Since the start of the captive breeding program, the highest numbers of frogs were released into suitable habitats on the SBNF within the past year.

The Institute is able to hatch and hold 400-500 tadpoles within the facility from year to year. Allowing tadpoles to develop into juvenile stages increases the chance of survival in the wild following release.

“In previous years, we were only capable of doing one release per year due to lack of reproduction,” said David Austin, forest biologist on the San Bernardino National Forest (SBNF). “However, this year, numbers in the captive breeding program exceeded the capacity of the facility,” Austin added. “The multiple releases this year, with both tadpoles and juveniles, will help vary the age classes of frogs in the wild.”

A mountain yellow-legged frog tadpole lies motionless in the creek bottom

Newly released mountain yellow-legged frog tadpole on September 9th, 2016, in City Creek, San Bernardino National Forest. Photo: Kim Boss

In 2015, 711 tadpoles were released into Fuller Mill Creek in the San Jacinto Mountains. In 2016, tadpoles, juveniles, and sub-adults were again released at multiple sites in Fuller Mill Creek and the North Fork San Jacinto River on May 27th, July 5th and September 29th. “Reliable data is not available yet, but detection of juveniles prior to the 2016 releases in Fuller Mill Creek and North Fork of the San Jacinto River may be evidence that mountain yellow-legged frogs are successfully breeding at both sites,” explains Ann Bowers, district wildlife biologist on the San Jacinto Ranger District of the SBNF.

In addition, for the first time, captive-bred tadpoles were released into City Creek in the San Bernardino Mountains on September 9th. Front Country Ranger District wildlife biologist Kim Boss is excited to have conducted the City Creek release. “This is an excellent step toward species recovery in a traditional habitat,” said Boss. “We look forward to a continued partnership that will lead to the sustainability of the MYLF and its diverse habitat.

Habitat Recovery Efforts on the SBNF

The SBNF has effectively managed species recovery and recreation together by incorporating creek closures during the season in which mountain yellow-legged frogs are active and by staffing key areas with seasonal hosts and biological technicians to keep visitors informed. Monitoring closure areas has doubled as an opportunity for public outreach, where SBNF staff and volunteers regularly interact with the public in a positive and proactive way. Repeat photos of closure areas in the San Jacinto Mountains, taken 15 years apart, indicate that habitat has been significantly improved and restored, allowing for ideal captive release site conditions.

Before and after photos of 2 locations in the closure area that show excellent habitat recovery

The Dark Canyon Campground closure area and habitat recovery over a 15-year interval since the closure was established in 2001. Photo credits – 2001 photos: A. Poopatanapong. 2015 re-takes: L. VanSant

With a common purpose, the US Forest Service and our partner agencies have made tremendous strides towards conservation and recovery of the mountain yellow-legged frog while providing a positive balance of recreation and other uses on the forest. This dynamic partnerships holds hope for this little-known southern California species.

The future of this promising recovery effort depends on continued agency collaboration and funding.

The next steps are securing new funding to continue this project and identifying additional re-introduction sites. To help with the recovery efforts, biologists ask that the public respect these small closures to avoid contaminating the streams.

Populations of the mountain yellow-legged frog can also be found on the Angeles NF.