Behavior and diet data collected from i) GPS video camera collars and ii) fecal samples collected from individuals from the Fortymile Caribou Herd

Summer diets are crucial for large herbivores in the subarctic and are affected by weather, harassment from insects and a variety of environmental changes linked to climate. Yet understanding foraging behavior and diet of large herbivores is challenging in the subarctic because of their remote ranges. We used GPS video-camera collars to observe behaviors and summer diets of the migratory Fortymile Caribou Herd (Rangifer tarandus granti) across Alaska, USA and the Yukon, Canada. First, we characterized caribou behavior. Second, we tested if videos could be used to quantify changes in the probability of eating events. Third, we estimated summer diets at the finest taxonomic resolution possible through videos. Finally, we compared summer diet estimates from video collars to microhistological analysis of fecal pellets. We classified 18,134 videos from 30 female caribou over two summers (2018 – 2019). Caribou behaviors included eating (mean = 43.5%), ruminating (25.6%), travelling (14.0%), stationary awake (11.3%) and napping (5.1%). Eating was restricted by insect harassment. We classified forage(s) consumed in 5,549 videos where diet composition (monthly) highlighted a strong tradeoff between lichens and shrubs; shrubs dominated diets in June and July when lichen use declined. We identified 63 species, 70 genus and 33 family groups of summer forages from videos. After adjusting for digestibility, monthly estimates of diet composition were strongly correlated at the scale of the forage functional type (i.e., forage groups comprised of forbs, graminoids, mosses, shrubs, and lichens; r = 0.79, p &lt; 0.01). Using video collars, we identified i) a pronounced tradeoff in summer foraging between lichens and shrubs and ii) the costs of insect harassment on eating. Understanding caribou foraging ecology is needed to plan for their long-term conservation across the circumpolar north and video collars can provide a powerful approach across remote regions.夏季日粮对亚北极地区大型植食动物至关重要，其受到天气、昆虫骚扰以及诸多与气候相关的环境变化的影响。然而由于亚北极地区大型植食动物的活动范围极为偏远，对其觅食行为与日粮组成的研究颇具挑战。本研究依托GPS视频项圈（GPS video-camera collars），对美国阿拉斯加州与加拿大育空地区的迁徙型四十英里驯鹿种群（Rangifer tarandus granti）的行为模式与夏季日粮展开观测。本研究依次开展四项工作：其一，刻画驯鹿的行为谱；其二，验证能否通过视频量化进食事件发生概率的变化；其三，依托视频以尽可能精细的分类学分辨率估算夏季日粮组成；其四，将视频项圈获取的夏季日粮估算结果与粪便颗粒显微组织学分析结果进行比对。本研究对2018至2019年两个夏季、30头雌性驯鹿的18134段视频进行了行为分类。驯鹿的行为类型包括进食（占比均值43.5%）、反刍（25.6%）、移动（14.0%）、静息清醒（11.3%）与休憩打盹（5.1%）。进食行为会受到昆虫骚扰的抑制。本研究对5549段记录了取食行为的视频进行了饲草分类，月度日粮组成分析显示，驯鹿在取食地衣与灌木之间存在显著的权衡：6月与7月时，地利用量下降，灌木成为日粮的主导组分。通过视频分析，本研究共识别出夏季饲草的63个物种、70个属以及33个科类群。在校正消化率后，月度日粮组成估算结果在饲草功能型（即由阔叶草本、禾草类、苔藓类、灌木与地衣构成的饲草类群）层面呈现出极强的相关性（r = 0.79, p < 0.01）。依托视频项圈，本研究明确了两点核心发现：其一，驯鹿夏季觅食在地衣与灌木之间存在显著的取食权衡；其二，昆虫骚扰对进食行为带来的成本代价。为制定环北极地区驯鹿的长期保护规划，亟需深入理解其觅食生态学，而视频项圈技术可为偏远地区的相关研究提供强有力的研究手段。