Mountain yellow-legged frog tadpoles released on the San Jacinto Ranger District

A biologist empties a bucket of Mountain Yellow-legged frogs into the waters of Fuller Mill Creek.

On Friday, May 22, 2020, approximately 711 mountain yellow-legged frog tadpoles were released into Fuller Mill Creek by personnel from the US Geological Survey (USGS) and the San Diego Zoo. The mountain yellow-legged frog, or MYLF, is a federally endangered species, and occurs in only a few locations on the San Bernardino and Angeles National Forests. These 35-45 days old tadpoles, shown in the bucket about the size of a figure nail, were raised at the San Diego Zoo, as part of the captive breeding program to help with the recovery of the species. The San Diego facility can only hold around 400 tadpoles to rear or grow to juvenile frogs, and due to over 1100 tadpoles successfully hatching this year, the additional tadpoles had to be released early into the wild. They were transported in buckets with small portable aerators to keep oxygen in the water for the 3-hour trip from the zoo. The water was slowly acclimated to the stream water and temperature by slowing mixing stream water into the buckets prior to release.

The MYLF captive breeding program, a partnership between various federal, state, and zoological societies, for over 5 years have been successfully breeding and releasing egg masses, tadpoles, and juvenile 2-3 year old frogs at the James Reserve/Hall Canyon.

The USGS will be monitoring the release area over the next couple of months to see how many tadpoles are still in the release area. Survivability of tadpoles to juvenile frogs is less than 5%, due to various factors, thus only about 30-40 of these tadpoles are expected to make it through the first year. This low survival rate is part of the reason these frogs are endangered. Other factors include loss of habitat, predation, and from infection from chytrid which is a type of fungus which occurs naturally in most of the streams in our area.

The Forest has a closure order in place for the protection of all occupied MYLF habitat on the forest:  City Creek on the Front Country RD and NF San Jacinto River/Dark Canyon, Hall Canyon, and Fuller Mill Creeks on the San Jacinto RD.