Scientific name: Rana boylii
Taxonomic classification
- Kingdom: Animalia
- Phylum: Chordata
- Class: Amphibia
- Order: Anura
- Family: Ranidae (true frogs)
- Genus: Rana
- Species: Rana boylii
Common names
- Foothill yellow‑legged frog
- Boylii frog
- Sierra yellow‑legged frog (regional variation)
Physical description
- Medium‑sized true frog, typically 5–8 cm (2–3 in) in body length.
- Dorsal coloration ranges from brown to olive with darker blotches; ventral surfaces are lighter, often yellowish.
- Distinctive bright yellow coloration on the underside of the hind limbs and feet, giving rise to the common name.
- Skin is relatively smooth with subtle dorsal ridges.
Distribution
- Endemic to the western United States, primarily in California and parts of Oregon.
- Occupies foothill and low‑elevation stream habitats within the Sierra Nevada, the Coast Ranges, and the Cascade foothills.
- Historically recorded from the Sacramento, San Joaquin, and Klamath River basins, among others.
Habitat
- Prefers cold, clear, fast‑flowing streams and rivers with gravel or rocky substrates.
- Often found at elevations between 300 and 2,500 m (1,000–8,200 ft).
- Requires riparian vegetation for shelter and foraging.
Life cycle and behavior
- Breeding occurs in late winter to early spring, synchronized with seasonal snowmelt and increased stream flow.
- Males call from stream banks; the advertisement call consists of a series of short, low‑frequency notes.
- Eggs are deposited in shallow, well‑oxygenated water, attached to submerged rocks or gravel.
- Tadpoles are adapted to fast‑flowing water; they possess a streamlined body and a muscular tail.
- Metamorphosis typically occurs within 2–3 months, after which juveniles disperse into adjacent terrestrial habitats.
Diet
- Adults are opportunistic predators, feeding on aquatic and terrestrial invertebrates such as insects, larvae, worms, and small crustaceans.
- Tadpoles graze on periphyton, algae, and detritus.
Conservation status
- Listed as “Near Threatened” on the IUCN Red List (assessment 2022).
- Designated as “Threatened” under the California Endangered Species Act.
- Primary threats include:
- Habitat alteration from water diversion, dam construction, and channelization.
- Sedimentation and pollution affecting water quality.
- Invasive species (e.g., non‑native fish predation on eggs and larvae).
- Climate change impacting stream flow regimes and temperature.
- Conservation measures involve habitat protection, restoration of natural flow regimes, monitoring population trends, and public education.
Research and monitoring
- Ongoing studies focus on population genetics, delineation of distinct management units, and the species’ response to hydrological changes.
- Amphibian monitoring programs in California often include the foothill yellow‑legged frog as an indicator species for stream health.
References
- IUCN SSC Amphibian Specialist Group. 2022. Rana boylii. The IUCN Red List of Threatened Species 2022.
- U.S. Fish and Wildlife Service. Species Profile: Foothill Yellow‑legged Frog (Rana boylii).
- California Department of Fish and Wildlife. “Foothill Yellow‑legged Frog (Rana boylii) Conservation Plan.”
All information presented is derived from established scientific and conservation sources.
