Unmanned Aerial Vehicles (UAVs), or drones, have recently emerged as a
relatively affordable and accessible method for studying wildlife.
Vertical Take-off and Landing (VTOL) UAVs are appropriate for
morphometric, behavioural, abundance and demographic studies of marine
mammals, providing a stable, nonintrusive and highly manoeuvrable
platform. Previous studies using VTOL UAVs have been conducted on
various marine mammal species, but specific studies regarding
behavioural responses to these devices are limited and scarce. The aim
of this study was to evaluate the immediate behavioural responses of
common (Delphinus delphis) and bottlenose (Tursiops truncatus)
dolphins to a VTOL UAV flown at different altitudes. A multirotor
(quadcopter) UAV with an attached GoPro camera was used. Once a dolphin
group was located, the UAV was flown at a starting height of 50 m
directly above the group, subsequently descending 5 m every 30 s until
reaching 5 m. We assessed three behavioural responses to a VTOL UAV at
different heights: (i) direction changes, (ii) swimming speed and (iii)
diving. Responses by D. delphis (n = 15) and T. truncatus (n = 10) groups were analysed separately. There were no significant responses of T. truncatus to any of the studied variables. For D. delphis,
however, there were statistically significant changes in direction when
the UAV was flown at a height of 5 m. Our results indicate that UAVs do
not induce immediate behavioural responses in common or bottlenose
dolphins when flown at heights > 5 m, demonstrating that the use of
VTOL UAVs to study dolphins has minimal impact on the animals. However,
we advise the use of the precautionary principle when interpreting these
results as characteristics of this study site (e.g., high
whale-watching activity) may have habituated dolphins to anthropogenic
disturbance.
Feel free to email me if you have any questions.
Best regards,
Joana Castro
