Comparison of eDNA metabarcoding to camera trapping for terrestrial
vertebrate monitoring highlights the importance of substrate type,
frequency of sampling and animal size
Abstract
Fauna biodiversity assessments often rely on traditional biomonitoring
techniques such as camera traps, which may have biases that lead to gaps
in biodiversity data. Environmental DNA (eDNA) has emerged as a new
source of biodiversity data that may account for these gaps. However,
eDNA biodiversity assessment remains relatively untested in terrestrial
environments. We compared vertebrate detections using two independent
monitoring methods: camera traps and eDNA (n = 160), across two sites in
south-western Australia. We also investigated the suitability of tree
hollow sediment as a source of eDNA, and the effect of other factors
(visitation frequency and timing, animal size) on vertebrate species
detectability. We detected 31 taxa with eDNA and 47 with camera traps of
which 14 overlapped (12 mammals and 2 birds). Tree hollow sediment
detected a wider range of biodiversity than did soil at the entrance of
the hollow. By comparing camera trap data with eDNA sequence reads, we
were able to detect animals with eDNA that had visited the area up to
two months prior to sample collection, with a negative correlation
between sequence read amount and days since last recorded detection via
camera. “Large” animals (>3kg) detected via camera were
associated with significantly higher sequence read amounts than smaller
animals. Our results show the effect of substrate selection, frequency
of sampling and animal size, on eDNA based surveys. If the aim is to
detect broad taxon diversity eDNA based approaches need to be
complemented by traditional vertebrate survey methods.