Foothill Yellow-legged Frog - Appearance

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 the legs, which may extend to their abdomen, but this characteristic is faint or absent in young frogs. There is a triangular, buff-colored patch on the snout, and, unlike other frogs in the Rana genus, there is no eye stripe. The throat and chest are often boldly mottled; moreover, the species has indistinct dorso-lateral skin folds and granular skin. Males of this species develop a nuptial pad on their thumb base during the breeding season. These frogs can be identified by their rough skin, horizontal pupils, fully webbed hind feet, and its habit to jump into moving water. However, tadpoles of this species resemble that of their rival, the Western Toad or Bufo boreas. The R. boylii as tadpoles have fairly flattened tails that lack color at the end and are the tallest in the midsection. The mouth of the tadpoles are made for suction to rocks with lip, known as labial, teeth rows used for scraping algae and diatoms, unicellular algae with cells walls that contain silica, off of the rocks they are clinging to. 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.