Data from: Integrating multiple technologies to understand the foraging behaviour of Hawaiian monk seals

The objective of this research was to investigate and describe the foraging behaviour of monk seals in the main Hawaiian Islands. Specifically, our goal was to identify a metric to classify foraging behaviour from telemetry instruments. We deployed accelerometers, seal-mounted cameras and GPS tags on six monk seals during 2012–2014 on the islands of Molokai, Kauai and Oahu. We used pitch, calculated from the accelerometer, to identify search events and thus classify foraging dives. A search event and consequent ‘foraging dive’ occurred when the pitch was greater than or equal to 70° at a depth less than or equal to −3 m. By integrating data from the accelerometers with video and GPS, we were able to ground-truth this classification method and identify environmental variables associated with each foraging dive. We used Bayesian logistic regression to identify the variables that influenced search events. Dive depth, body motion (mean overall dynamic body acceleration during the dive) and proximity to the sea floor were the best predictors of search events for these seals. Search events typically occurred on long, deep dives, with more time spent at the bottom (more than 50% bottom time). We can now identify where monk seals are foraging in the main Hawaiian Islands (MHI) and what covariates influence foraging behaviour in this region. This increased understanding will inform management strategies and supplement outreach and recovery efforts.

本研究旨在调查并描述夏威夷主群岛（Main Hawaiian Islands，下文简称MHI）僧海豹的觅食行为。具体而言，本研究的目标是确立一项可通过遥测仪器（telemetry instruments）对僧海豹觅食行为进行分类的量化指标。2012至2014年间，研究团队在莫洛凯岛、考艾岛及瓦胡岛的6只僧海豹身上部署了加速度计（accelerometers）、佩戴式相机与GPS标签（GPS tags）。研究人员利用从加速度计计算得到的俯仰角（pitch）识别搜索事件，以此对觅食潜水行为进行分类：当海豹所处水深≤-3米且俯仰角≥70°时，即判定发生了一次搜索事件，对应此次行为为“觅食潜水”。通过整合加速度计、拍摄视频与GPS采集的数据，本研究得以对该分类方法开展实地校验，并识别出与每一次觅食潜水相关的环境变量。本研究采用贝叶斯逻辑回归（Bayesian logistic regression）筛选出影响搜索事件发生的变量，结果显示，潜水深度、身体运动状态（潜水期间的平均总体动态身体加速度（overall dynamic body acceleration））以及与海底的相对距离，是预测该类海豹搜索事件的最优因子。搜索事件通常发生于时长较长的深潜过程中，且海豹会在水底花费超过总潜水时长50%的时间。如今我们已能够明确夏威夷主群岛内僧海豹的觅食区域，以及该区域内影响其觅食行为的各类协变量（covariates）。此项研究获得的更深入认知，可为相关管理策略制定提供科学依据，并对宣教推广与种群恢复工作形成有效补充。