Drone Up! Quantifying Whale Behavior From a New Perspective Improves Observational Capacity

Leigh G Torres,Leila Lemos,Sharon L Nieukirk,Todd E Chandler

doi:10.3389/fmars.2018.00319

Abstract

From our traditional boat-based horizontal perspective, marine megafauna behavioral observations are typically limited to animal surfacings. Achieving an aerial perspective has been restricted to brief helicopter or airplane based observations that are costly, noisy and risky. The emergence of commercial small unmanned aerial systems (UAS) has significantly reduced these constraints, and provide a stable, relatively quiet and inexpensive platform that enables replicate observations for prolonged periods with minimal disturbance. The potential of UAS for behavioral observation appears immense, yet quantitative methods of video analysis and proof of utility as an observational tool are required. We use UAS footage of gray whales foraging in coastal waters of Oregon, USA to develop analysis methods, assess behavioral impacts caused by UAS, determine the change in observation time enabled by UAS, and describe unique behaviors observed via UAS. Boat-based behavioral observations from 53 gray whale sightings between May and October 2016 were compared to behavioral data extracted from video analysis of UAS flights during those sightings. We used a DJI Phantom 3 Pro or 4 Advanced, recorded video from an altitude ≥25m, and detected no behavioral response by whales to the UAS. Two experienced whale ethologists conducted UAS video behavioral analysis, including tabulation of whale behavior states and events, and whale surface time and whale visible time (total time the whale was visible including underwater). UAS provided three times more observational capacity than boat-based observations alone (300 vs. 103 minutes). When observation time is accounted for, UAS data provided greater observations of all primary behavior states (travel, forage, social, rest) relative to boat-based data, especially forage, which increased by three times. Furthermore, UAS enable documentation of multiple novel gray whale foraging tactics (e.g., headstands: n=58; side-swimming: n=17; jaw snapping and flexing: n= 10) and 33 social events (nursing, pair coordinated surfacings) not identified in the field. This study demonstrates the significant added value of UAS to marine megafauna behavior and ecological studies. With technological advances, robust study designs, and effective analytical tools, we foresee increased UAS applications to marine megafauna studies to elucidate foraging strategies, habitat associations, social patterns, and response to human disturbance.

Highlights

With the decreasing cost of commercial small unmanned aerial systems (UAS; known as ‘drones’) and increasing accessibility and reliability of platforms, there has been a rapid expansion of UAS applications to marine megafauna research throughout the 2010s
We examine the potential benefit of UAS to cetacean behavioral studies and describe limitations, pitfalls, and methodological pathways to encourage the development of the robust application of UAS to expand our understanding of cetacean behavior
Behavioral data from 53 gray whale sightings were compared to UAS flights during those sightings

Summary

Introduction

With the decreasing cost of commercial small unmanned aerial systems (UAS; known as ‘drones’) and increasing accessibility and reliability of platforms, there has been a rapid expansion of UAS applications to marine megafauna research throughout the 2010s In this period, UAS has been applied to a range of marine megafauna, including studies on body condition of cetaceans (Christiansen et al, 2016a; Dawson et al, 2017; Burnett et al, in press) and pinnipeds (Goebel et al, 2015; Krause et al, 2017) through photogrammetry techniques; population, density and distribution estimates of pinnipeds (Goebel et al, 2015; Johnston et al, 2017), cetaceans (Hodgson et al, 2017), seabirds (Goebel et al, 2015), sirenia (Hodgson et al, 2013), and turtles (Sykora-Bodie et al, 2017); photo-identification studies of pinnipeds (Pomeroy et al, 2015) and cetaceans (Koski et al, 2015); and exhalent sample collection of cetacean blows (Acevedo-Whitehouse et al, 2010; Pirotta et al, 2017). No study has applied UAS to investigate the behavioral ecology of marine mammals

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