The foothill yellow-legged frog (Rana boylii) is a small-sized frog from the genus Rana in the family Ranidae. This species can be found in the Coast Ranges from northern Oregon, through California, and into Baja California, Mexico as well as in the foothills of the Sierra Nevada and southern Cascade Range in California. The foothill yellow-legged frog is a Federal Species of Concern and California State Endangered. Appearance The foothill yellow-legged frog has a grey, brown, or reddish dorsum, or the back of the frog. It is commonly spotted or mottled, but occasionally is plainly colored. Adults have yellow coloration under their legs, which may extend to their abdomens, but this characteristic is faint or absent in young frogs. A triangular, buff-colored patch occurs on the snout, and, unlike other frogs in the genus, there is no eye stripe. The throat and chest are often boldly mottled; and the species has indistinct dorsolateral skin folds and granular skin. Males of this species develop nuptial pads on their thumb bases during the breeding season. These frogs can be identified by their rough skin, horizontal pupils, fully webbed hind feet, and their habit of jumping into moving water. Tadpoles of this species, though, resemble those of the western toad, Bufo boreas. R. boylii as tadpoles have fairly flattened tails that lack color at the end and are the tallest in the midsection. The mouths of the tadpoles are made for suction to rocks, with labial teeth rows used for scraping algae and diatoms, unicellular algae with cells walls that contain silica, off of the rocks to which they are clinging. The mouth of the young R. boylii is also helpful in identifying it from B. boreas because the young foothill yellow-legged frogs develop more defined teeth rows after three weeks, while their counterparts do not. Both the Columbia spotted frog and the Cascades frog, also part of the genus Rana, live in the northern regions of this frog's territory. Food sources Food supplies, such as algae the tadpoles eat, also affect the sexual maturity of the species. Reportedly, the "amount of protein in different algae, can affect size at and time to metamorphosis" and "these food effects may be mediated through diet-induced changes in thyroid function", which means the food the tadpoles ingest dictates the changes in the thyroid gland's production of certain proteins. Tadpoles most commonly feed on algae, diatoms, and