The mountain yellow-legged frog was once one of the most abundant vertebrates in the Sierra Nevada. The flash of its yellow legs could be seen and the echo of its croaking could be heard across the Sierra’s alpine lakes, even those nestled at 12,000 feet that contain watery habitats typically too cold for amphibians. Unfortunately, that empire began to crumble as long ago as 1850 when non-native trout were first transplanted into some of those lakes to increase fishing opportunities.