Sierra Nevada mountain yellow-legged frog (Rana muscosa), Range: Sierra Nevada of California and Nevada. Once the most abundant amphibian in the Sierra Nevada, this hardy frog is now extinct in more than 93 percent of its original range. Primarily decimated by the introduction of nonnative predator fish to its high-elevation pond and lake homes, the yellow-legged frog will also undoubtedly be impacted by climate change. Yellow-legged frogs remain in the tadpole stage for three to four years, whi