DOI: 10.5061/dryad.5dv41ns6c
title: The behavioural responses of Lasiorhinus latifrons to night-time and daytime drone flight

description: The use of drones in wildlife research and management is
 increasing. Recent evidence has demonstrated the impact of drones
 on animal behavior but the response of nocturnal animals to drone flight
 remains unknown. Utilising a lightweight commercial drone, the behavioral
 response of southern hairy-nosed wombats (Lasiorhinus latifrons)
 to drone flights was observed at Kooloola Station, Swan Reach, South
 Australia. All wombats flown over during both day and
 night flights responded behaviorally to the presence of drones.
 The response differed based on time of day. The most common night-time
 behavior elicited by drone flight was retreat, compared to stationary
 alertness behavior observed for daytime drone flights. The behavioral
 response of the wombats increased as flight altitude decreased. The marked
 difference of behavior between day and night indicates that this has
 implications for studies using drones. The behavior observed during
 flights was altered due to the presence of the drone, and therefore shrewd
 study design is important (i.e.acclimation period to drone flight).
 Considering the sensory adaptations of the target species and how this may
 impact its behavioral response when flying at night is essential.
description: Preliminary flights (n = 16 flights, n = 30 total
 transects) were flown over wombats using the
 same transect methodology and at the same flight altitudes used in the
 final data collection. The preliminary flights were conducted to refine
 the methodology and ensure reliable capture of data. The final data
 collection occurred during 3 consecutive days in October with similar
 weather conditions to reduce variability of responses.
 A DJI Phantom 4 Pro™ drone was used during the final data
 collection. The drone flew horizontally at 5 metres per second (m/s)
 directly over the located wombat/s at predetermined altitudes (100m, 60m,
 30m). After take-off, the drone immediately ascended to an altitude of
 100m and flew along a transect over the wombat to a distance of
 approximately 100m past the wombat and back to the launch position. If the
 wombat did not retreat to its burrow, the drone descended to the next
 lowest altitude (60m) and the same horizontal transect was flown. This
 process was repeated until; (a) the wombat retreated into its warren, or
 (b) all flight altitudes were exhausted. A single transect constituted
 flying over the wombat to the predetermined distance past the wombat
 (100m) and back to the original launch position.
 Sixty-eight flights (n = 127 transects) were undertaken over
 wombats during daytime and night-time, with 59 flights occurring during
 the night (n = 101 transects) and 9 taking place during day (n = 26
 transects). Flights were on average 20 minutes apart during the day
 and approximately 14 minutes apart during the night. Despite some
 flights occurring a short distance apart from each other (n = 100m), the
 temporal separation between flights was long enough for wombats to revert
 to their original behavior before location with the spotlight.
 Locating wombats for daytime drone flights (5:30pm to
 7:30pm) Searching for wombats for daytime drone flight
 experiments involved driving a 4WD vehicle slowly along tracks on the
 property searching for wombats on, or near, their warrens. Once a wombat
 was spotted the vehicle was positioned behind the closest bush and
 stopped, to ensure the wombat was not disturbed prior to launching the
 drone. The drone was then deployed at a safe distance from the vehicle and
 out of sight of the wombat. The observers stood motionless and
 semi-obscured from the wombat to avoid any disturbance and monitored the
 animal’s behavior through binoculars (8x40mm). Locating
 wombats for night-time flights (9:30pm to 2am)
 Searching for wombats at night involved two observers walking
 along the vehicular tracks at the station using a spotlight (Ledlenser™
 H14R.2 headlamp; Low 60 lumens, Power 450 lumens and Boost 1000 lumens) to
 scan for wombats on or near their warrens. The drone pilots followed
 behind at a distance of approximately 100m. If a wombat was identified, a
 red light was used to signal to the drone pilots to stop and set up ready
 to launch the drone. Whilst this was happening, the spotlight was shone on
 the wombat for ~2 minutes to ensure that any change in behavior observed
 following deployment of the drone was caused by the presence of the drone
 and the sound it created, and not associated with the spotlight. Previous
 experience spotlighting wombats over multiple surveys across decades has
 indicated that wombats are highly tolerant of spotlights, of which poor
 eyesight can be attributed to. Typically no change is observed in
 behavior following detection by spotlight unless the animal is within a
 close proximity (~25m). Detailed notes and observations
 were made associated with each drone flight. Information was
 collected on: time, flight altitude, location, moon phase, latitude and
 longitude of drone launch site on the property, Warren ID, distance
 between the drone launch site and the wombat (Yukon™ Extend LRS-1000
 Rangefinder) and wombat behavior. Wombat behavior was
 classified as follows:  No behavioral response
 exhibited (0)  Alert but stationary (1)
  Alert with movement in any direction, but did not retreat to
 burrow (2)  Alert and retreat into burrow (3)
 SHN wombat behavior was categorised and tabulated into an
 ethogram. Behavioral observations using binoculars (8x40mm) occurred
 approximately 40-120m from the wombat/s during drone flights. Other
 anthropogenic sources of disturbance, such as cars driving on a road
 adjacent to the property, or planes flying overhead, were noted but were
 rarely present. In the event these disturbances occurred, flights were
 postponed until vehicles were clear of the area and the study environment
 returned to its natural state. A wombat was considered alert if it was
 observed to lift its head and prick up its ears as a result of the
 disturbance activity (e.g. drone noise, spotlight, vehicle noise). If
 there was no change in behavior pre and post drone flight, the wombat was
 considered to have been unaffected behaviorally by drone flight.
 All statistical analysis of wombat behavior taken from the field
 behavioral observations were undertaken in the R environment. A general
 linear mixed effects model (GLMM) was used to evaluate the significance
 of the covariates time of day, flight altitude, moon
 phase and distance between launch site and the wombat. None of these
 covariates except flight altitude had a significant effect on wombat
 behavior. In order to evaluate the response of wombats
 to drone flight altitude, we used the ‘survival’ package. In this
 instance, ‘survival’ denotes a wombat remaining above ground and not
 retreating into its burrow. ‘Survival’ probability was calculated as a
 response to drone altitude, but not for time. This analogy allows for the
 estimation of confidence intervals around the wombats staying above ground
 and to separate between night and day responses.
description: All data is presented as is and is ready to analyse.