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1. Surveys for environmental DNA (eDNA) can provide an efficient and effective means of detecting aquatic organisms in various types of aquatic systems. 2. In the summer of 2017, the efficacy of a new, integrated eDNA backpack sampler to detect two native amphibians (Rana sierrae and R. cascadae) at risk was tested in complex mountain meadows in California. Samples were collected at 65 locations in 15 meadows where the target species were known to be present or were historically present. 3. Collection and preservation of individual samples took less than 10 min on average. Environmental DNA analysis methods detected each species at all meadows with visual detections (N = 11) except one with one frog seen away from sampling sites. Bayesian multi-scale occupancy modelling indicated that conditional detection probabilities at the sample level ranged from 0.30 (CL 0.07-0.65) at meadow heads where no frogs were observed during visual surveys to 0.93 (CL 0.77-1.00) at the meadow foot with at least one frog observed in the vicinity. 4. Compared with visual surveys, eDNA methods more frequently detected amphibians at the sampling-location scale. The improvement in detection using eDNA methods was most pronounced for samples collected at the downstream ends of meadows where water converges, where eDNA methods detected target species at 10 of 11 occupied meadows. 5. These results suggest that the addition of eDNA sampling to visual surveys in mountain meadows will improve survey accuracy and increase the probability of detecting rare frogs.

Effective management of wildlife populations threatened by disease requires accurate predictions about the consequences of intervention. However, generating such predictions is challenging, especially for organisms with complex life histories that are also threatened by climate change, such as montane amphibians. Cascades frogs (Rana cascadae) in northern California have experienced dramatic declines associated with the fungal pathogen Batrachochytrium dendrobatidis (Bd), and remnant populations are also threatened by changing climate conditions. We evaluated the population-level impacts of treating Cascades frog metamorphs with the antifungal chemical itraconazole using a field experiment and population simulations. We explored the influence of larval habitat on these treatment effects by including metamorphs from different larval habitat types. We found that frogs treated with itraconazole were more than four times more likely to survive their first winter than untreated controls and had reduced Bd infection intensity compared to other surviving frogs from the same cohort in the following year. We also found an effect of larval habitat type on Bd infection in recently metamorphosed frogs, with the lowest levels of infection occurring in frogs emerging from larval habitats that tend to be intermediate in temperature and drying rate. Applying the differential apparent overwinter survival of treated and untreated metamorphs to population projections suggests that intermittent antifungal treatment of metamorphs has the potential to restore population viability. Our results indicate that in situ treatment of individual hosts may be a useful component of a comprehensive management strategy to reduce the risk of pathogen-mediated population declines and extirpations.

Disturbances are part of the natural dynamics of Earth's ecosystems, with these events more common now in the Anthropocene. Yet metrics for calibrating these impacts and measuring an ecosystem's capacity to recover are lacking. Highway construction in 1989 to bypass Prairie Creek Redwoods State Park in California resulted in storm‐driven infusion of exposed sediments into five streams; five nearby streams that were not intersected by the bypass construction were not affected by this event and served as controls for a natural experiment. A second large storm event in 1995 contributed sediment loads into all ten streams resulting in a disturbance gradient that allowed us to examine the effects of repeated sediment disturbances. We evaluated the impacts of these stresses on three resident stream amphibian species in 1990 and again in 1996. In 1990, the impacted streams had sixfold higher pool sediment loads and significantly lower larval tailed frog (Ascaphus truei) densities and lower densities of coastal giant salamanders (Dicamptodon tenebrosus) and southern torrent salamanders (Rhyacotriton variegatus) compared with the un‐impacted streams. During the six years between these storm events, pool bowl sediment loads increased 14‐fold in the previously un‐impacted streams and threefold in the previously impacted streams. Larval tailed frogs and torrent salamanders further declined in both sets of streams in 1996 although non‐significantly. In contrast, giant salamander densities increased in both stream sets. Of the three species, giant salamanders appeared the most resistant to the depositional events, while the other two species appeared to decline relative to the intensity of the sediment disturbances but still persist. We believe these results demonstrate the usefulness of these three amphibians as metrics for measuring the effects of this common disturbance type on the ecological resilience of stream networks in this and other temperate northwest forest ecosystems.