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Mountain Yellow-legged Frog (Rana muscosa) Fact Sheet: Population & Conservation Status

Conservation Status

IUCN Status

  • Endangered  (2008 assessment) (Hammerson G. 2008)

CITES Status

  • Not listed (as of May 2019) (UNEP 2019)

United States Endangered Species Act

  • Endangered


 History of Conservation Efforts

  • Identification of two distinct populations: northern and southern California
    • 2002: Given Endangered Species Status by USFWS
    • 2006: Designation of Critical Habitat by USFWS; 8,283 acres in portions of Los Angeles, Riverside, and San Bernardino counties
    • 1996-2004: Listed as Vulnerable by IUCN
    • 2006: Listed as Critically Endangered by IUCN
    • 2008: Listed as Endangered by IUCN

By 2003, fewer than 200 individuals remained in the wild

  • Survey of 150 historical distribution sites (Backlin 2013)
    • Nine small populations were detected
    • Abundance estimates were small (1–55 adults per population).
    • Data indicated most of the remaining populations had fewer than 10 pairs of adults.
  • Reintroductions of individuals bred in managed care supplementing reproduction in wild populations

SDZG Institute for Conservation Research

  • Leading efforts to study the reproduction and natural history of this species, with ultimate goal of preventing its extinction
  • Hatch eggs and raise young frogs in managed care
    • Release into the wild
  • Working to improve husbandry and managed care breeding protocols
    • Simulate seasonal temperature changes (hibernation cues)
    • Simulate natural light cycles
    • Study nutritional requirements
  • Use assisted reproduction techniques (e.g., hormone therapies and in vitro fertilization)
  • Partnerships with the California Department of Fish and Wildlife, U.S. Forest Service, U.S. Fish and Wildlife Service, U.S. Department of Agriculture, U.S. Geological Survey, and Los Angeles Zoo
  • Preserving genes in The Frozen Zoo®
  • Studying embryo and tadpole development
  • See Managed Care

Threats to Survival

(Hammerson 2008)


  • Chytrid fungus
  • Red-leg disease/syndrome


  • Predation on tadpoles by non-native fish
    • specially introduced trout

Environmental effects

  • Drought
  • Fire (San Diego Zoo Global Press Releases)
    • Habitat saturated in ash and debris
  • Loss of genetic vigor due to population isolation and inbreeding
  • Air and water contamination
    • Agricultural chemicals/pesticides
    • Low pH and elevated aluminum concentrations
    • Mining
    • Human disturbance of wildlife areas
  • Threats described by IUCN (International Union for Conservation of Nature)

Endangered Frogs Reintroduced

Learn how San Diego Zoo Global researchers raise endangered mountain yellow-legged froglets for reintroduction into the wild.

© San Diego Zoo Global. All rights reserved.

SDZG ICR Recovery Program

Jeff Lemm at ICR checks Mountain Yellow-legged frog eggs

ICR Senior Research Coordinator, Jeff Lemm, checks a clutch of Mountain Yellow-Legged Frog eggs.

The San Diego Zoo Institute for Conservation Research (ICR) has been breeding, raising and reintroducing frogs into historical native habitat since 2010.

Image credit: Ken Bohn, © San Diego Zoo Global. All rights reserved.



Mountain Yellow-legged frog being released into the wild

Release into Fuller Mill Creek.

Image credit: Ken Bohn, © San Diego Zoo Global. All rights reserved.

Page Citations

USFWS (2002)
USFWS (2006)
IUCN (2004)
IUCN (2006)
IUCN (2008)
Backlin (2013)
Fellers et al. (2001)
Vredenburg et al. (2008)

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