Elk Home Range - Shamrock - 2022-2023 [ds3085]

The project lead for the collection of this data was Carrington Hilson. Elk (1 adult female) were captured and equipped with GPS collars (Lotek Iridium) transmitting data from 2022-2023. The Shamrock herd does not migrate between traditional summer and winter seasonal ranges. Therefore, annual home ranges were modeled using year-round data to demarcate high use areas in lieu of modeling the specific winter ranges commonly seen in other ungulate analyses in California. GPS locations were fixed between 1-7 hour intervals in the dataset. To improve the quality of the data set as per Bjørneraas et al. (2010), the GPS data were filtered prior to analysis to remove locations which were: i) further from either the previous point or subsequent point than an individual pronghorn is able to travel in the elapsed time, ii) forming spikes in the movement trajectory based on outgoing and incoming speeds and turning angles sharper than a predefined threshold , or iii) fixed in 2D space and visually assessed as a bad fix by the analyst. The methodology used for this migration analysis allowed for the mapping of the herd’s home range. Brownian bridge movement models (BBMMs; Sawyer et al. 2009) were constructed with GPS collar data from 1 elk, including 1 annual home range sequence, location, date, time, and average location error as inputs in Migration Mapper. BBMMs were produced at a spatial resolution of 50 m using a sequential fix interval of less than 27 hours. Home range is visualized as the 50th percentile contour (high use) and the 99th percentile contour of the year-round utilization distribution. Home range designations for this herd may expand with a larger sample.本数据集的采集项目负责人为卡林顿·希尔森（Carrington Hilson）。研究人员捕捉了1头成年雌性马鹿（Elk），为其佩戴了Lotek铱星GPS项圈（Lotek Iridium），该设备于2022年至2023年期间持续传输定位数据。沙姆罗克鹿群（Shamrock herd）不会在传统的夏季与冬季活动范围之间进行迁徙，因此本研究未沿用加州其他有蹄类动物分析中常见的单独建模冬季活动范围的方法，而是采用全年定位数据对年度家域（home range）进行建模，以此划定该种群的高频使用区域。本数据集中的GPS定位点采样间隔为1至7小时。为提升数据集质量，参照比约纳拉斯等（Bjørneraas et al., 2010）的研究方案，分析前对GPS定位数据开展了滤波处理，移除以下三类定位点：一是在相邻定位的间隔时长内，距离前一或后一定位点的距离超出单只叉角羚（pronghorn）所能移动的最大距离的点位；二是基于进出速度与转弯角度形成运动轨迹尖峰，且转弯角度超出预设阈值的点位；三是仅采用二维空间固定解，且经分析师目视评估为劣质定位的点位。本次迁徙分析所采用的方法可实现该种群家域的可视化制图。研究基于1头佩戴GPS项圈的马鹿的定位数据，构建了布朗运动桥移动模型（Brownian bridge movement models, BBMMs; 索耶等，Sawyer et al., 2009），将1组年度家域序列、定位坐标、日期、时间以及平均定位误差作为输入参数导入Migration Mapper软件。该模型以50米的空间分辨率、小于27小时的连续定位间隔生成结果。家域通过全年利用分布的50%分位数等高线（高频使用区）与99%分位数等高线进行可视化呈现。该种群的家域划定范围可能会随着后续样本量的扩大而进一步拓展。