Elk Home Range - Elk Creek - 2021 [ds2984]

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 in 2021. The Elk Creek 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 1-6 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. Large water bodies were clipped from the final output. 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.

本数据集的项目负责人为卡林顿·希尔森（Carrington Hilson）。2021年，研究人员捕获1头成年雌性马鹿（Elk），并为其佩戴Lotek Iridium型号GPS项圈以传输数据。该埃尔克溪种群不会在传统的夏季与冬季活动范围间进行迁徙，因此相较于加州多数有蹄类动物分析中常规针对特定冬季活动范围的建模思路，本研究使用全年数据对年度家域进行建模，以此划定高频使用区域。本数据集内的GPS定位点固定间隔为1至6小时。为参照比约纳拉斯等（Bjørneraas et al., 2010）的方法提升数据集质量，分析前研究人员对GPS数据开展了过滤处理，移除以下三类定位点：i）在间隔时长内超出单只叉角羚（pronghorn）可行进距离的、与前一或后一定位点距离过远的点；ii）基于出射速度、入射速度及超过预设阈值的急转弯角度而形成运动轨迹尖峰的点；iii）采用二维空间固定且经分析人员目视评估为无效的定位点。本次迁徙分析所采用的方法可实现该种群家域的制图。研究以1头佩戴GPS项圈的马鹿的GPS数据为输入，在迁徙映射器（Migration Mapper）中构建了布朗桥运动模型（Brownian bridge movement models, BBMMs；Sawyer et al., 2009），输入参数包含1组年度家域序列、定位坐标、日期、时间及平均定位误差。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。最终输出结果已裁剪掉大型水体区域。家域以全年利用分布的50%百分位等高线（高频使用区）与99%百分位等高线进行可视化展示。该种群的家域划定范围可随样本量扩大而进一步拓展。