Amphibians
Amphibians are in major decline throughout the world, and Yosemite and Sequoia/Kings National Parks are no exception. Researchers are struggling to determine why. The answer appears to be complex and many-pronged. Partly the problem is nonnative species, partly an introduced devastating fungus, and perhaps partly factors as yet to be determined.
There are 11 native amphibian species found in Yosemite. The only non-native amphibian in the park is the American bullfrog (Lithobates catesbeiana), a keen predator of native animals such as frogs, toads, salamanders, small mammals, snakes, turtles, birds, and bats.
Non-native fish are also a serious threat to frogs in Yosemite, Sequoia/Kings Canyon, and throughout the Sierra. Fish did not occur naturally in lakes above about 6,000ft, but were introduced by humans for sports fishing. The effect on mountain aquatic ecosystems was devastating, including serious depredation of tadpoles and declines of frog populations.
Three of Yosemite's amphibians are found only in California's Sierra Nevada: the Yosemite toad (Anaxyrus canorus), the Mount Lyell Salamander (Hydromantes platycephalis), and the Sierra Nevada yellow-legged frog (Rana sierrae). The Sierra Nevada yellow-legged frog was 
once abundant at high elevations, but has been listed as federally endangered since 2014. Over 95% of these frogs have disappeared.
While introduced fish and bullfrogs are part of the problem, even more devastating has been the spread of a deadly chytrid fungus called Batrachochytrium dendrobatidis (Bd) that has been causing amphibian declines and extinctions globally. As part of a tremendous restoration effort, Bd-resistant yellow-legged frogs have been raised, transported by helicopter, and reintroduced to several lakes that have undergone invasive trout eradication. Researchers estimate that these Sierra Nevada yellow-legged frog populations will be self-sustaining within the next ten years.
More Information:
National Park Service- Amphibian Checklist: http://www.nps.gov/yose/learn/nature/amphibian-species.htm
National Park Service- Amphibians: http://www.nps.gov/yose/learn/nature/amphibians.htm
National Park Service- Sierra Nevada Yellow-Legged Frog: http://www.nps.gov/yose/learn/nature/frog.htm
National Park Service- Yosemite Restoring Endangered Yellow-legged Frogs to Alpine Lakes: http://www.nps.gov/yose/learn/news/frogrestoration.htm
Peden, Colin. KALW Local Public Radio- Frogs in danger of croaking: fighting a fungal epidemic: http://kalw.org/post/frogs-danger-croaking-fighting-fungal-epidemic#stream/0
