The project leads for the collection of this data were Josh Bush and Tom Batter. Elk (7 adult females, 8 adult males) from the Cortina Ridge herd were captured and equipped with Lotek GPS collars (LifeCycle 800 GlobalStar, Lotek Wireless, Newmarket, Ontario, Canada), transmitting data from 2017-2022. The study area was within the Bear Valley Elk Management Unit, east of Route 20 and southeast of Mendocino National Forest. Route 20 appears to be a barrier to movement, as these elk do not overlap with the Bear Creek Ranch – Antelope Valley herd on the other side of the road. The Cortina Ridge herd contains short distance, elevation-based movements likely due to seasonal habitat conditions, but this herd does not migrate between traditional summer and winter seasonal ranges. Instead, the herd displays a residential pattern, slowly moving up or down elevational gradients. 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 at 13-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 elk 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 analysis allowed for the mapping of the herd’s annual range based on a small sample. Brownian Bridge Movement Models (BBMMs; Sawyer et al. 2009) were constructed with GPS collar data from 12 elk in total, including 31 year-long sequences, location, date, time, and average location error as inputs in Migration Mapper to assess annual range. Annual range BBMMs were produced at a spatial resolution of 50 m using a sequential fix interval of less than 27 hours. Population-level annual range designations for this herd may expand with a larger sample, filling in some of the gaps between high-use annual range polygons in the map. Annual range is visualized as the 50th percentile contour (high use) and the 99th percentile contour of the year-round utilization distribution.