Assessing the Behavioural Responses of Small Cetaceans to Unmanned Aerial Vehicles

Francisco O. Borges,Rui Rosa,Joana Castro,Heidi C. Pearson,Marina I. Laborde,André Cid

doi:10.3390/rs13010156

Abstract

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.

Highlights

Introduction nal affiliationsUnmanned Aerial Systems (UASs) have recently emerged as a relatively inexpensive and accessible method for studying wildlife [1,2,3]
The present study evaluated the immediate behavioural responses of common and bottlenose dolphins to a Unmanned Aerial Vehicles (UAVs) flown at different heights
While previous research examined the impact of UAVs on bottlenose dolphins [18,20], to our knowledge, this is the first study to assess the impact of Vertical Take-off and Landing (VTOL) UAVs on common dolphins

Summary

Introduction

Introduction nal affiliationsUnmanned Aerial Systems (UASs) have recently emerged as a relatively inexpensive and accessible method for studying wildlife [1,2,3]. Aerial Vehicle (UAV or drone), a launch and recovery system, a video camera payload mounted to the UAV and a ground control system [4] These devices constitute an alternative to manned aerial surveys, having both improved manoeuvrability and less intrusion than manned aircraft, while providing high-resolution video with lower risk to human life and at a potentially reduced financial cost [1,5,6,7]. UAVs are a category of UAS that are usually smaller and have the ability to hover in flight and take-off and land without a runway [1] This provides a stable, nonintrusive and highly manoeuvrable platform for the detailed study of an individual or small groups of animals [1,2]. In comparison to boats, manned aerial surveys and fixed-wing

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