Hidden under logs or in dense vegetation, amphibians are among the least seen wildlife of the park. You may have heard a Pacific chorus frog chirping near a creek, or seen the California newt on its yearly migration. Sodden areas near creeks and marshes are the best place to find amphibians. In locations such as Big Lagoon near Muir Beach, soft clear balls of amphibian eggs attach to emergent vegetation, and male frogs call out to potential mates. Or in forested areas, a check under fallen logs will most likely turn up slender salamanders. Amphibians are highly sensitive to pollution, and a close eye on these animals can alert park managers to potential contaminants in wetlands and in the atmosphere.

The threatened California red-legged frog has been extirpated from 70 percent of its former range. Threats to this species include urban encroachment, construction of reservoirs and water diversions, introduction of non-native predators and competitors such as the bullfrog, livestock grazing, and habitat fragmentation.