Tracking wildlife energy dynamics with unoccupied aircraft systems and 3-dimensional photogrammetry

We present a novel application using unoccupied aircraft systems (UAS; drones) for structure-from-motion three-dimensional (3-D) photogrammetry of multiple, free-ranging animals simultaneously. Pinnipeds reliably haul-out on shore for pupping and breeding each year, accompanied by dramatic female-to-pup mass transfer over a short lactation period and males lose mass while defending mating territories. This provides a tractable study system for validating the use of UAS as a non-invasive tool for tracking energy dynamics in wild populations. UAS imagery of grey seals (Halichoerus grypus) was collected at Saddle Island, Nova Scotia. A multirotor UAS was piloted in 360-degree orbits around relatively dense animal aggregations and georeferenced images were used for construction of a 3-D point cloud, orthomosaic, and Digital Surface Model for animal volumetric measurements. Directly following UAS survey, a subset of adult females were hand-measured (morphometrics, blubber depth, n=21 hand...我们提出了一项创新应用，借助无人航空器系统（Unoccupied Aircraft Systems, UAS；无人机），可同步对多只野生自由活动动物开展运动恢复结构三维（3-D）摄影测量。鳍足类动物每年都会规律性地上岸栖息以开展产仔与繁殖活动，在此期间雌性个体与幼崽之间会在较短的哺乳期内发生显著的体重转移，而雄性个体则会在保卫交配领地的过程中出现体重下降。这为验证无人机作为非侵入式工具以追踪野生种群能量动态提供了一个可操作性强的研究体系。 研究团队在新斯科舍省萨德尔岛采集了灰海豹（Halichoerus grypus）的无人机影像。研究人员操控多旋翼无人机对相对密集的动物集群进行360度环绕拍摄，并利用地理参考影像构建了三维点云、正射影像图以及数字表面模型，用于开展动物体积测量。在完成无人机航拍调查后即刻，研究人员选取了部分成年雌性灰海豹开展手工测量（涵盖形态测量学指标、脂肪层厚度，样本量n=21……）