eDNA sampled from stream networks correlates with camera trap detection rates of terrestrial mammals

Biodiversity monitoring delivers vital information to those making
conservation decisions. Comprehensively measuring terrestrial biodiversity
usually requires costly methods that can rarely be deployed at large
spatial scales over multiple time periods, limiting conservation
efficiency. Here we investigated the capacity of environmental DNA (eDNA)
from stream water samples to survey terrestrial mammal diversity at
multiple spatial scales within a large catchment. We compared biodiversity
information recovered using an eDNA metabarcoding approach with data from
a dense camera trap survey, as well as the sampling costs of both methods.
Via the sampling of large volumes of water from the two largest streams
that drained the study area, eDNA metabarcoding provided information on
the presence and detection probabilities of 35 mammal taxa, 25% more than
camera traps and for half the cost. While eDNA metabarcoding had limited
capacity to detect felid species and provide individual-level demographic
information, it is a cost-efficient method for large-scale monitoring of
terrestrial mammals that can offer sufficient information to solve many
conservation problems.