Introduction
Curbing worldwide wildlife population declines will necessitate the
protection of their habitat (Tilman et al. 2017). Aside from political
willingness, targeted habitat protection requires robust baseline
information about wildlife that use and occupy it. Collating such
information, however, remains a challenging and costly endeavour. To
tackle these problems, scientists have been working hard developing
innovative technologies that improve the cost-effectiveness and
scalability of data collection on wildlife assemblages, including
employing thermal drones, detection dogs, radars, camera traps
and bioacoustics devices (Cristescu et al. 2015, Hagens et al. 2018,
Hüppop et al. 2019, Beaver et al. 2020, Law et al. 2020). Whilst these
technologies have greatly expanded our capabilities to collect more
accurate baseline information on wildlife presence, the collation of
data on wildlife assemblages still comes at a significant technological
and human cost. To seek to identify the presence of multiple wildlife
species, ecologists must deploy a multitude of methods in synchrony,
which can include bioacoustics arrays, baited traits, camera traps and
human-led fauna transects (Mena et al. 2021). Hence, affordable and
scalable technology for the detection and monitoring of wildlife
assemblages across the landscape is a goal we should seek to achieve as
it would improve our ability to detect and track changes in wildlife
biodiversity patterns (e.g. species richness and community composition),
identify wildlife species or habitat of high conservation priority, and
underpin the development of successful management strategies.
Environmental DNA, known as eDNA is a promising technology to address
this issue. eDNA refers to the DNA that is shed into the environment as
wildlife move throughout the landscape, leaving previously unbeknownst
traces of their presence (Thomsen and Willerslev 2015). Already heavily
deployed in aquatic systems for at least two decades, the practicability
of utilising eDNA to detect species presence and assemblages is clearly
established (Hinz et al. 2022). For example, in 2016, aquatic eDNA
technology was first employed as part of environmental impact
assessments, demonstrating its capacity to meet regulatory standards and
obligations outlined by the International Association for Impact
Assessment (Hinz et al. 2022). However, to date, there is no such
established terrestrial analogue although recent studies have provided
promising results. Terrestrial wildlife’s eDNA has, for instance, been
detected from samples collected from spider webs, permafrost, blood,
snow, soil, honey and aerosol spray runoff (Andersen et al. 2012,
Folloni et al. 2012, Schnell et al. 2012, Valentin et al. 2018, Ribani
et al. 2020, Gregorič et al. 2022). Two most recent studies have also
demonstrated that airborne eDNA can be used to reassemble zoological
communities (Clare et al. 2022, Lynggaard et al. 2022). Together,
evidence suggest that airborne eDNA could be a promising avenue for the
identification of terrestrial wildlife assemblages as it is i)
non-invasive, ii) scalable, and iii) comparatively cost-effective given
it holds the potential to target species assemblages compared to single
species targeted approaches. The feasibility of using airborne eDNA to
identify wildlife assemblages under natural conditions remains yet to be
tested.
Here, we sought to test the applicability of airborne eDNA particles for
the detection of an endangered Australian species, the koala
(Phascolarctos cinereus ), and its co-occurring terrestrial
mammalian community in a natural setting. We demonstrate its successful
application to detecting koalas as well as other mammalian species in a
natural setting and discuss future steps for its continued improvement
and optimisation.