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The project lead for the collection of this data was Richard Shinn. Pronghorn (9 adult females) were captured and equipped with GPS collars (Sirtrack, Havelock North, NZ) transmitting data from 2019-2020. The Mount Dome herd contains short distance, elevation-based migrants, but this herd does not migrate between traditional summer and winter seasonal ranges. Instead, much of the herd displays a somewhat nomadic migratory tendency, slowly moving up or down elevational gradients. Some individuals used higher elevation areas throughout the summer, though this pattern was not ubiquitous. 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. The plateau extending south of Sardine Flat is highly used during winter by many of the collared animals, while the higher elevation flatlands between Klamath Lake Sump and Mount Dome are used in summer. Overall, a much smaller area is used than adjacent pronghorn herds in California, with much of the full home range extent being high use. GPS locations were fixed between 1-2 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 9 pronghorn, including 12 migration 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 and a fixed motion variance of 1000. Large water bodies were clipped from the final outputs. Home range is visualized as the 50th percentile contour (high use) and the 99th percentile contour of the year-round utilization distribution. Twelve years of collective movement data from 9 individuals were used to construct home ranges. Home range designations for this herd may expand with a larger sample.