Seddon, P. J. | Search bioRxiv

bioRxiv2025

Targeted Airborne eDNA Detection of Pest Wallabies: Effects of Sampler Type and Distance

Bennetts wallabies Notamacropus rufogriseus, introduced to New Zealand from Australia in the late 1800s, strongly exemplify the detection challenges posed by invasive terrestrial species that are rare, cryptic, and highly mobile. Across their invasive range, N. rufogriseus occupy large landscapes at low densities, making their surveillance challenging. Recent research has demonstrated that airborne environmental DNA (eDNA) can rapidly identify terrestrial vertebrate diversity in an area. Leveraging these findings, we investigate the utility of airborne eDNA for the targeted monitoring of N. rufogriseus, using a novel, probe-based quantitative PCR assay. The effects of filtration material, collection method (active versus passive), distance from the source, and environmental conditions were examined for their effects on airborne detection probability, using a captive population of wallabies in a controlled park setting. A total of 110 airborne samples were collected, 55 with active (battery-powered fan) samplers and 55 passive (non-powered) samplers, across six distinct experimental periods at distances of 0, 10, 100, and 1000 metres from the closest known source of wallaby DNA. Filters designed to capture coarse particles (>10 {micro}m) significantly improved detection rates and DNA recovery for actively collected samples, compared to filters targeting finer particles (1-10 {micro}m). Active samplers significantly outperformed passive samplers in overall detection rates, particularly at shorter ranges from the target. Distance from the source had a significant negative effect on detection probability. Detection rates declined sharply beyond 10 metres but remained possible up to 1 kilometre from the source for both collection methods. These findings demonstrate that airborne eDNA can detect terrestrial vertebrate species at ecologically relevant distances, supporting its potential for landscape-scale surveillance. Notably, these results underscore the importance of optimising sampler design when applying airborne eDNA for targeted species monitoring.

genetics↗

bioRxiv2022

Estimating home range and temporal space use variability reveals age-related differences in risk exposure for reintroduced parrots

Individual-level differences in animal spatial behaviour can lead to differential exposure to risk. We assessed the risk-exposure of a reintroduced population of k[a]k[a] (Nestor meridionalis) in a fenced reserve in New Zealand by GPS tracking 10 individuals and comparing the proportion of each individuals home range beyond the reserves fence in relation to age, sex, and fledging origin. To estimate dynamic space use, we used a sweeping window framework to estimate occurrence distributions from temporally overlapping snapshots. For each occurrence distribution, we calculated the proportion outside the reserves fence to assess temporal risk exposure, and the area, centroid and overlap to represent the behavioural pattern of space use. Home range area declined significantly and consistently with age, and the space use of juvenile k[a]k[a] was more dynamic, particularly in relation to positional changes of space use. The wider- ranging and more dynamic behaviour of younger k[a]k[a] resulted in consistently more time spent outside the reserve, which aligned with a higher number of incidental mortality observations. Quantifying both home range and dynamic space use is an effective approach to assess risk exposure, which can provide guidance for management interventions. We also emphasise the dynamic space use approach, which is flexible and can provide numerous insights towards a species spatial ecology.

ecology↗