Global efforts to conserve declining amphibian populations have necessitated the development of rapid, reliable, and targeted survey methods. Environmental DNA (eDNA) surveys offer alternative or complementary methods to traditional amphibian survey techniques. The California Tiger Salamander Ambystoma californiense (CTS) is endemic to California where it breeds in vernal pools. In the past 25 years, CTS has faced a 20.7 percent loss of known occurrences, largely through habitat loss, and is threatened by hybridization with an introduced congener. Protecting and managing remaining CTS populations relies on accurately monitoring changes in their spatial distribution. Current monitoring practices typically employ dip-net surveys, which are time-consuming and prone to false negative errors. To provide a new resource for monitoring and surveying larval CTS, we designed an assay and tested it on environmental samples collected from 29 vernal pools at two locations in California. We compared eDNA results to contemporaneous dip-net surveying results and found 100% agreement on the presence/absence surveys of larval CTS. In several instances we also detected the presence of CTS genetic material in the early spring months before larvae hatched, potentially offering a new, earlier detection option for this imperiled species. This assay provides a valuable, non-invasive molecular tool for monitoring the spatial distribution of CTS in vernal pools.

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