Elk Home Range - Gilbert - 2017-2021 [ds2986]

The project lead for the collection of this data was Carrington Hilson. Elk (4 adult females) were captured and equipped with GPS collars (Lotek Iridium) transmitting data from 2017-2021. The Gilbert 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 3 elk, including 5 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.本数据集的采集项目负责人为卡林顿·希尔森（Carrington Hilson）。研究人员捕获4头成年雌性马鹿（Elk），并为其佩戴Lotek Iridium GPS项圈，该设备于2017至2021年间持续传输定位数据。吉尔伯特种群并不会在传统的夏季与冬季活动范围之间进行迁徙。因此，本研究采用全年定位数据对年度家域进行建模，以划定高频使用区域，而非如加州其他有蹄类动物研究那般，单独针对冬季活动范围开展建模。数据集中的GPS定位采样间隔为1至6小时。为提升数据集质量，参照比约纳拉斯等（Bjørneraas et al., 2010）的研究方法，分析前对GPS数据进行了滤波处理，以剔除以下三类定位点：其一，在间隔时长内，超出单个叉角羚（pronghorn）可移动距离的点位；其二，基于出射与入射速度计算，且转弯角度超过预设阈值，在运动轨迹上形成尖峰的点位；其三，仅为二维固定解且经分析人员目视判定为无效定位的点位。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。研究基于3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），将5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软件进行计算。该模型的空间分辨率设置为50米，采用小于27小时的连续采样间隔生成结果。最终输出的可视化结果中已剔除大型水体区域。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。该种群的家域范围可能会随着样本量的扩大而进一步扩展。