Amphibians are animals with backbones (vertebrates) that spend a part of their life underwater and the remainder living on land. They are cold-blooded, meaning that they depend on the temperature of their environment to regulate their own internal temperature. Amphibians are distinguished from reptiles by their absence of scales (although some of them have scales imbedded under their skin). Amphibians are further distinguished by those that are voiceless and their larvae have no teeth (salamanders) and those that make noise and their larvae have teeth (frogs and toads).
Although the number of amphibian species is limited at Point Reyes, the rarity of species is notable. The highest densities of California red-legged frogs, for example, are located in riparian areas of Point Reyes. This species is now federally threatened but was once abundant throughout California and was the species of Mark Twain's legend of the jumping frog of Calaveras County. Globally, over 200 amphibian species have experienced recent population declines, with reports of 32 species extinctions. Data from California clearly document not just a decline in frog and toad populations, but extirpation of certain species throughout a significant portion of their range. Some of the reasons for this decline include factors related to the overall biodiversity crisis which includes: habitat destruction (alteration; fragmentation), introduced species, and overexploitation.
However, these are not the only reason for declines as they have also declined in relatively pristine' environments. The more complex and elusive mechanisms potentially underlying declines include climate change, UV-B radiation, chemical contaminants, infectious diseases, deformities, and any combination of any of these factors that may exacerbate negative conditions. Researchers are finding that there is not a single overarching cause for global declines, instead all of these factors are threatening amphibian populations to a greater or lesser extent.