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Mountain Yellow-legged Frog (Rana muscosa) Fact Sheet: Summary

Mountain Yellow-legged Frog (Rana muscosa) Fact Sheet

Mountain Yellow-Legged Frog (Rana muscosa)

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


Taxonomy Physical Characteristics

Describer (Date): Camp (1917)

Kingdom: Animalia

Phylum: Chordata

Class: Amphibia

Order: Anura

Family: Ranidae

Genus: Rana

Species: R. muscosa

Body Length
Male snout-vent length: 2.20 in (56 mm)
Female snout-vent length: 2.52 in (64 mm)

Sexual Dimorphism
Females larger
Males have nuptial pad on forefeet

Back green or brown, with spotted pattern
Front white or yellow

Distribution & Status Behavior & Ecology

Southern California in San Jacinto,
San Bernadino and San Jacinto mountains

Mountain streams and ponds with
riparian (bank) vegetation

IUCN Status

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

CITES Appendix

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

Population in Wild
Less than 200 individuals

Activity Cycle
Diurnal (active during the day)

Highly aquatic, hops on land

Tadpoles eat algae, small insects and aquatic larvae of insect species.
Adults eat insects.

Trout eat tadpoles.

Interspecies Interactions
Trout interrupt pathways between foraging
and breeding sites.

Reproduction & Development Species Highlights

Males and females migrate to ponds for breeding

Occurs just after ice melts, April-May

Eggs laid late spring to early summer

Clutch Size
100-1000 eggs per egg mass

Time to hatching
From 5-6 weeks

Metamorphosis requires at least one season of overwintering, 2-3 years

About 14 years

Featured Facts
  • Among the largest of North American frogs, reaching over 3 inches
  • Metamorphosis in the wild may occur within 6 months, but may take up to 2-3 years, depending on environmental conditions
  • Endangered
  • Threats include disease, predators, and environmental factors
  • San Diego Zoo Global's Conservation for Research Institute (CRI) leading Mountain Yellow-legged Frog recovery efforts; began in 2006
  • First successfully bred in managed care in 2009
  • Reintroductions to the wild since 2010


About This Fact Sheet

© 2016 San Diego Zoo Global.

How to cite: Mountain Yellow-Legged Frog (Rana muscosa) Fact Sheet. c2016. San Diego (CA): San Diego Zoo Global; [accessed YYYY Mmm dd]. mountainyellow-leggedfrog
(note: replace YYYY Mmm dd with date accessed, e.g., 2017 Jan 15)

Disclaimer: Although San Diego Zoo Global makes every attempt to provide accurate information, some of the facts provided may become outdated or replaced by new research findings. Questions and comments may be addressed to


Thank you to Dr. Natalie Calatayud for providing expert content review of this fact sheet.

At the time of this writing, Dr. Calatayud serves as a Postdoctoral Associate in the Institute for Conservation Research’s Reproductive Physiology Division. Her research interests include reproduction, endocrinology, and nutrition in frogs and toads. Natalie’s main research focus is the recovery and reintroduction of the endangered mountain yellow-legged frog. In addition, she acts as a consultant for the Colorado Division of Parks and Wildlife’s boreal toad recovery team.

Dr. Calatayud earned her Bachelor’s degree in Zoology from the University of Manchester and her Doctoral degree in Reproductive Physiology and Molecular Biology at Melbourne University.

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