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.
Range-wide Persistence of the Endangered Arroyo Toad (Anaxyrus californicus) for 20+ Years Following a General Warming Trend and Prolonged Drought
