This species of frog is endemic to California in the USA. You can find them in the San Jacinto Mountains, San Gabriel Mountains in Southern California, San Bernardino Mountains, and the southern Sierra Nevada.
These frogs are found in riverbanks, meadow streams, isolated pools. They seem to prefer sloping backs with vegetation and are typically found near a water source. They shelter in winter under ledges and in deep underwater crevices. Females deposit eggs by attaching them to rocks, vegetation or gravel in permanent freshwater sources like streams or lakes. They feed in a variety of invertebrates like beetles, ants, bees, wasps, flies, dragonflies, etc.
Rana muscosa is a small (1.6-3.5 inches in length) aquatic frog. From above, they have a yellowish to reddish-brown color with brown or black markings that resemble lichen. Its toe tips have a dusky color with the underside of the hind limbs and (sometimes) the belly displaying yellow or orange. This yellow coloration often widens out to the forelimbs. Dorsolateral folds are present but may sometimes be indistinct. Tadpoles are typically black to dark brown and are relatively large (exceeding 3.9 inches in total length).
Learn more with Schechter Natural History's Guide to Reptiles and Amphibians