Cheadle Center for Biodiversity and Ecological Restoration

Santa Cruz Island harbors two congeneric slender salamanders: the island-endemic Batrachoseps pacificus, and Batrachoseps nigriventris. Over two years, habitat transect and coverboard surveys were conducted, recording microhabitat characteristics, collecting morphometric data, and swabbing for the chytrid fungal pathogen Batrachochytrium dendrobatidis (Bd), a globally significant amphibian disease responsible for widespread declines and extinctions in amphibian populations worldwide. Results indicate spatial variation in population distribution and differences between species in body size and morphology. At syntopic sites, body size differed between the two species but not when comparing sites where only one species occurred. Bd was detected in over 25% of each species. Differences were detected in habitat use, with B. nigriventris being present more evenly across surveyed habitat types, and also across a broader range of microclimate. These findings suggest another explanation for disproportionate spatial distributions than microhabitat, and raise concerns about disease dynamics within this isolated island system, where even low prevalence pathogens like Bd could have disproportionate long-term impacts on endemic amphibian populations.