Abstract
Wildlife monitoring is a crucial component of conservation management,
with reliable field surveys being important for trend analysis and
population viability modelling. Unoccupied aircraft systems (UAS), also
known as drones, are rapidly supplanting manned aircraft for aerial
wildlife counts. Here we investigated and compared the impacts of drone
presence on two large terrestrial mammals from Tasmania,
Australia—Bennett’s wallaby (Notamacropus rufogriseus), and
Forester kangaroo (Macropus giganteus tasmaniensis) —using a
commercial quadcopter model: DJI Phantom 4 Pro. Further, a ground bird,
the domestic chicken (Gallus gallus domesticus), was used as a
model organism to further investigate behavioural responses of ‘aerial
aware’ species to drones. We found that M. giganteus tasmaniensis
and N. rufogriseus started to exhibit noticeable changes in
behaviour, including evasion, when the drone motor sound exceeded
~50 decibels (dB) as heard from the ground (at flight
altitudes of 30 – 50 m). At lower sound levels (48 dB and below, above
50 m), the animal’s response was minimal. The response of G.
gallus domesticus to the drone was remarkably similar to that of the
Macropus species, despite the species generally being more
susceptible to, and instinctively vigilant against drone-sized aerial
predators such as raptors. This study has established the baseline
information required to understand the limits of drone operations, in
terms of target disturbance, for macropod surveys.