Like many amphibians, the Yosemite Toad is declining. Yet the causes have been difficult to diagnose because population surveys are very difficult to conduct. The Yosemite Toad breeds immediately after snowmelt in high-elevation meadows in California’s central Sierra Nevada, which means accessing sites when adult toads are most conspicuous is very difficult.
In spring 2021, I conducted a pilot study which showed that we can deploy autonomous recording units before the snow melts, retrieve them later in the summer, and then use BirdNET to identify the vocalizations of Yosemite toads, as well as Pacific chorus frogs, and possibly Great Gray Owls (another threatened Sierra meadow specialist). The ongoing US Forest Service toad monitoring project conducts mark-recapture surveys at a few breeding areas, and the next step is comparing vocalization counts to adult population counts to derive an acoustic-based population index that could be applied more broadly.
In spring 2022, with the support of a Discovery Expedition Grant awarded by The Explorers Club, I conducted a six-day expedition into the High Sierra to deploy 14 recording units across an area that is only rarely surveyed for the toad. That work was featured briefly on Discovery’s new show “Tales from the Explorers Club”.
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Check out this short video about the 2021 fieldwork.