Yosemite is home to a small variety of amphibians as compared to more temperate or tropical climates. This may be due in part to past glacial activity, and in part the park's Mediterranean climate which includes hot, dry summers and cold, wet winters.
The Sierra newt spends most of the year on land. It retreats to moist natural and human-made refuges, such as rodent burrows, seepages, rock fissures, mine shafts, and rotten logs during the dry season. Moisture that comes with the first falls rains brings this species out to breed. Newts are most visible between November and May when they are migrating to and from their breeding sites in nearby ponds, streams, and rivers. During this time, park visitors may see the newts crossing roads or trails. While at their breeding sites, adult males develop a smooth skin and a flattened tail. This allows them to thrive in the aquatic environment. The rest of the year, their skin is thick, rough, and relatively unvascularized to reduce the amount of water lost to evaporation while living on land.
The diminutive Pacific treefrog is Yosemite's most common frog species. You can find them throughout the park, at all elevations and in nearly all habitats. Treefrogs are even found in cracks on the face of El Capitan.You are most likely to hear treefrogs calling in meadows and ponds during the spring.
The Sierra Nevada yellow-legged frog was once the most abundant vertebrate found in Yosemite’s high-country lakes and streams. Visitors used to describe finding frogs in such great numbers that “it was difficult to walk without stepping on them.” Populations have since declined approximately 95% in the Sierra Nevada, including in Yosemite. Recent surveys in 2005-2007 determined that the species is still declinging and on a trajectory toward extinction. Because of this, the frog has been listed as an Endangered species for protection under the Federal Endangered Species Act. The introduction on nonnative trout and amphibian chytrid fungus are the primary reasons for their decline.
The Yosemite toad has also experienced serious declines, losing at least 50% of their populations. This once common wet meadow species is rarely encountered by the public today; however, its uniquely different coloration between the sexes, musical call, and stately toad behavior is a treat for those fortunate enough to encounter them. Visitors to Yosemite's high-country have described the Yosemite toad's call as a strikingly clear, high-pitched trill with its mellow notes being a "pleasing addition to the chorus of bird songs just after the snow leaves."
The nonnative bullfrog is a voracious predator that has been implicated in the decline of many native animals. Bullfrogs eat anything they can get their mouth around including: native frogs, toads, salamanders, small mammals, snakes, turtles, even birds and bats. Bullfrogs probably played a part in the loss of populations of western pond turtles and California red-legged frogs in the park. The California red-legged frog no longer occurs in the park. Because bullfrogs have a huge impact on the native wildlife, we have been eradicating them from Yosemite Valley.
Scientists published two papers on the effects of chytrid fungus on the mountain yellow-legged frog species complex, which includes the Sierra Nevada yellow-legged frog (Rana sierrae), and the Sierra Madre yellow-legged frog (Rana muscosa). The Sierra Nevada yellow-legged frog can be found in Yosemite.