We conducted surveys for the Endangered Sierra Madre yellow-legged frog Rana muscosa throughout southern California to evaluate the current distribution and status of the species. Surveys were conducted during 2000-2009 at 150 unique streams and lakes within the San Gabriel, San Bernardino, San Jacinto, and Palomar mountains of southern California. Only nine small, geographically isolated populations were detected across the four mountain ranges, and all tested positive for the amphibian chytrid fungus Batrachochytrium dendrobatidis. Our data show that when R. muscosa is known to be present it is easily detectable (89%) in a single visit during the frog's active season. We estimate that only 166 adult frogs remained in the wild in 2009. Our research indicates that R. muscosa populations in southern California are threatened by natural and stochastic events and may become extirpated in the near future unless there is some intervention to save them.

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Prolonged drought due to climate change has negatively impacted amphibians in southern California, U.S.A. Due to the severity and length of the current drought, agencies and researchers had growing concern for the persistence of the arroyo toad (Anaxyrus californicus), an endangered endemic amphibian in this region. Range-wide

Conservation translocations, the human-mediated movement and release of a living organism for a conservation benefit, are increasingly recommended in species’ recovery plans as a technique for mitigating population declines or augmenting genetic diversity. However, translocation protocols for species with broad distributions may require regionally specific considerations to increase success, as environmental gradients may pose different constraints on population establishment and persistence in different parts of the range. Here we report on ongoing, genetically informed translocations of a threatened amphibian, California red-legged frog (Rana draytonii), from Baja California, México, to extirpated parts of the range in southern California in the United States, where contemporary stressors related to urbanization, invasive species, and aridification add to the natural environmental challenges already present for amphibians at this ‘warm edge’ of the range. We describe the collaborative binational planning required to jumpstart the effort, the fine-tuning of protocols for collection, transport, headstarting, and release of individuals, and results of multiple translocations, where time will tell whether the successes to date have reached their full potential. The steps outlined in this paper can serve as a template to inform future conservation translocations of imperiled amphibians across the U.S./México border, where the phylogenetics, historical biogeography and future habitat availability of a focal species are blind to political boundaries and critical to guiding recovery actions across the range.

Climate change and prolonged drought have negatively impacted amphibians in southern California, U.S.A. Due to the severe drought from 2012–2016, agencies and researchers had growing concern for the persistence of the arroyo toad (Anaxyrus californicus), an endangered endemic amphibian in this region. Range-wide surveys for this species had not been conducted for at least 20 years. In 2017–2020 we conducted collaborative surveys for arroyo toads at historical locations. We surveyed 87 of the 115 total sites having historical records and confirmed that the arroyo toad is currently extant in 60 of 87 sites and 19 of 25 historically occupied watersheds. Only detection/non-detection and not population size was recorded, therefore potential declines at the population level could not be assessed. In other amphibian species, body condition has been documented to decrease with a decrease in water availability. To further investigate the drought’s impact on this species, we calculated an average body condition index annually for arroyo toads using allometric measurements recorded from 1996–present. This index was plotted against precipitation records over time. Our data show that body condition did not significantly change during drought years, but hydro-regulation may be masking an effect. Our study suggests that this species shows some resiliency to climate change and drought, and that mitigating invasive species, hydro-modification, and other anthropogenic drivers may currently be the most beneficial strategy for toad conservation. Arroyo toad conservation actions may also provide simultaneous benefits to several other native species that share the same habitat.