Elk Home Range - Gold Bluff Beach - 2017-2021 [ds2987]

The project lead for the collection of this data was Carrington Hilson. Elk (2 adult females) were captured and equipped with GPS collars (Lotek Iridium) transmitting data from 2017-2021. The Gold Bluff Beach 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 2 elk, including 6 annual home range sequences, 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.本数据集采集项目的负责人为卡林顿·希尔森（Carrington Hilson）。研究人员捕获2头成年雌性马鹿（Elk），为其佩戴Lotek Iridium型号的GPS项圈（GPS collar），该设备于2017年至2021年间持续传输定位数据。戈尔布拉夫滩种群（Gold Bluff Beach herd）不会在传统的夏季与冬季活动范围之间进行季节性迁徙。因此，本研究采用全年观测数据对年度家域进行建模，以划定高频活动区域，替代了加利福尼亚州其他有蹄类动物（ungulate）研究中常见的针对特定冬季活动范围的建模思路。本数据集内的GPS定位点设置为1至6小时间隔。为提升数据集质量，参照比约纳拉斯等人（Bjørneraas et al., 2010）的研究方法，分析前对GPS数据进行滤波处理，以剔除以下三类定位点：i）在对应间隔时长内超出单只叉角羚（pronghorn）最大移动距离的点位；ii）基于出射与入射速度计算、且转弯角度超出预设阈值的运动轨迹尖峰点位；iii）仅采用二维固定解且经分析人员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绘制。本研究基于2头马鹿的GPS项圈数据，构建了布朗桥运动模型（Brownian bridge movement models, BBMMs；Sawyer et al., 2009），并将6组年度家域序列、定位坐标、采集日期、时间及平均定位误差作为输入参数导入迁移映射器（Migration Mapper）。布朗桥运动模型以50米的空间分辨率、小于27小时的连续定位间隔生成。最终输出结果已剔除大型水体区域。该种群的家域通过全年利用分布的50%置信等高线（高频活动区）与99%置信等高线进行可视化展示。该种群的家域划定范围可能会随着样本量的扩大而进一步拓展。