May 18, 2010

Captive-bred Frogs Released into the Wild for the First Time

The southern mountain yellow-legged frog (Rana muscosa) inhabits lakes, ponds, and streams in the southern Sierra Nevada and southern California. The southern California Distinct Population Segment (DPS) was listed as "endangered" under the federal Endangered Species Act in 2002. This DPS currently contains fewer than 200 adult frogs and these remaining populations are at extreme risk of extinction due to a myriad of threats.

In response to the perilous status of this southern California DPS, scientists from the U.S. Geological Survey and San Diego Zoo have been working to develop an indoor captive breeding population the could eventually produce sufficient offspring for release into the wild. In an effort to stimulate frog breeding, this spring captive adult frogs were refrigerated for several weeks to simulate winter conditions. Once temperatures were increased frogs quickly began breeding, resulting in the production of numerous egg masses. 

In mid-April several of these egg masses were moved to a creek within the James San Jacinto Mountains Reserve, a reserve managed by the University of California. This is the first time that captive-bred mountain yellow-legged frogs have been released into the wild, and represents an important milestone in the recovery of frogs in this DPS. Time will tell how well the released animals survive. 

In addition to aiding the conservation of mountain yellow-legged frogs in southern California, these efforts have also produced a wealth of information regarding the breeding of these frogs in captivity. Whether we'll ever need these techniques for restoring mountain yellow-legged frogs in the Sierra Nevada remains to be seen but it is nice to have these methods already worked out. I continue to believe that one of the highest conservation priorities for Sierra Nevada frogs is to develop several outdoor captive populations of frogs in artificial ponds at an accessible location. Such populations are much less expensive to maintain than indoor captive populations (frogs don't need to be fed, water doesn't need to be changed, etc.) and would provide lots of offspring for use in research and conservation. All we need is a few ponds. Efforts to identify suitable ponds are ongoing.

Back to The Mountain Yellow-legged Frog Site.


  1. I'm on the El Dorado NF now, let me know what criteria for ponds you are looking for and how I can help. Rob Grasso

  2. Roland, on the Eldorado NF now, let me know if you have interest for pond sites here and the criteria you are looking for. Rob Grasso

  3. Hi Rob. The ideal situation would be 2-4 perennial ponds located in close proximity to each other and close to a road. To ensure that the ponds don't freeze or dry, ponds >3 m deep would be best. In addition, being able to surround the ponds with drift fencing to prevent frog emigration would be valuable.