Environmental DNA and wildlife camera traps uncover complimentary vertebrate visitation patterns at freshwater granite rock-holes

Freshwater ecosystems are in decline globally. In Australia, threatening processes include invasive species, increasing drought frequency, climate change and changes to land use, all of which have been associated with declining vertebrate diversity, particularly in Australia’s arid interior. Efficient monitoring tools are required to effectively monitor and conserve freshwater ecosystems and their associated vertebrate communities. Environmental DNA (eDNA) metabarcoding is one tool that shows promise for monitoring these systems, but knowledge of how eDNA data compares to more established ecological assessment techniques is limited. To address this knowledge gap, we sampled vertebrate eDNA from seven freshwater water bodies of proposed conservation importance in the Australian arid-lands, at three timepoints to measure visitation and compare our findings to camera trapping data at the same locations. Using eDNA we detected 19 species of vertebrates, including native species (such as macropods, wombats and emus) and invasive species (such as feral goats, cats and foxes). In contrast, camera traps detected 32 species, and was much more successful at detecting bird visitation than eDNA. These communities varied both spatially between rock-holes, and temporally, with summer collection periods being distinct from winter-spring. Our results demonstrate the success of eDNA metabarcoding as a tool for monitoring vertebrate visitation to arid-lands freshwater ecosystems that is complementary to more traditional survey methods such as wildlife camera trapping. Finally, we provide conservation recommendations for these vertebrate communities and discuss the efficacy of eDNA for monitoring freshwater resources in arid-lands environments.