Cascades Frog and eDNA Inventory at Lassen Volcanic National Park - Open Format Dataset

The Cascades frog (Rana cascadae) is one of two frog species known to occur historically in Lassen Volcanic National Park (LAVO) in Northern California. However, no Cascades frogs have been documented in LAVO for several decades, despite repeated surveys. Threats to the species include natural predators, introduction of fish into historically fishless habitats, diseases like fungal pathogens, airborne drift of pesticides from nearby agricultural areas, ultraviolet (UV-B) radiation, wildfires, and habitat loss from human development and climate change. Objectives of this project were to conduct surveys for Cascades frogs at LAVO using both visual encounter surveys (VES) and environmental DNA (eDNA) surveys at locations with potential for reintroduction, conduct VES and eDNA surveys for potential predators (rainbow trout, brook trout, brown trout, and leeches) to determine locations unsuitable for reintroduction, and to develop a suitability model to assess reintroduction potential within LAVO for Cascades frogs. Fifty locations around LAVO were sampled during this study. Suitability for Cascades frogs was ranked according to suitable vegetation availability, elevation, climatic factors, and perennial water availability. Projected climate data was used to derive future climate suitability for Cascades frogs within and around LAVO. No Cascades frog egg masses, larvae, or adults were detected during VES or eDNA sampling within LAVO in 2021. Pacific tree frogs were observed at 18 sites, indicating suitable larval frog habitat at these sites. At 12 of these 18 sites, trout were not detected with either VES or eDNA sampling and leeches were only detected in two locations. The eDNA survey did not appear to be an effective way to detect leeches, but this method was effective for trout species and Cascades frogs.