Miss Gracie Kroos1, Dr. Kristen Fernandes1,2, Prof. Philip Seddon4, Travis Ashcroft3, Prof. Neil Gemmell1
1University of Otago , Dunedin, Aotearoa / New Zealand, 2Department of Biodiversity, Conservation and Attractions, Perth, Australia, 3Department of Zoology, University of Otago, Dunedin, New Zealand, 4Ministry for Primary Industries, Hamilton, Aotearoa / New Zealand
Biography:
Gracie Kroos is based at the University of Otago in New Zealand. As part of her PhD, she focused on building practical tools for species monitoring, including the development and testing of airborne environmental DNA methods to detect invasive terrestrial species.
Abstract:
Airborne environmental DNA (eDNA) is increasingly recognised as a transformative approach for terrestrial conservation, but significant knowledge gaps currently hinder operational uptake, especially the detection capability at low population densities. Here, we investigated the airborne eDNA sampling effort required to reduce the risk of missed detections (false negatives) to ≤5%. We used species-specific qPCR assays to detect invasive marsupials, Bennett's and dama wallabies (Notamacropus rufogriseus and Notamacropus eugenii) across two New Zealand sites differing in target species and estimated population densities. The first site supported a confirmed low-density population of Bennett's wallabies (0.0029–0.0071 wallabies/ha) as established by camera-trap monitoring. The second site was assessed via ground-based surveillance to have moderate densities of dama wallabies. We deployed fan-powered sampling devices capable of 360-degree rotation to collect 60 airborne eDNA samples at each site, using coarse fibreglass filters to capture airborne particles. Airborne eDNA sampling successfully detected target wallaby species at each of the low-density and moderate-density sites, but the moderate-density site yielded more positive detections with higher concentrations of target species DNA in positive samples. Traditional ground-based surveillance efforts before and after eDNA sampling supported our findings. Overall, we demonstrate the utility of airborne eDNA sampling to detect rare targets across terrestrial landscapes, while highlighting the need for strong spatial, temporal, and technical replication for confidence in detection outcomes. Our findings have implications for biosecurity and conservation managers seeking non-invasive, sensitive surveillance tools for terrestrial species detection where traditional methods may be inefficient or prohibitively resource-intensive.