Mule Deer Migration Corridors - Carson River - 2012-2019 [ds2888]

The project lead for the collection of this data in California was Terri Weist. She, along with Danielle Walsh, Shelly Blair, and other personnel, captured 30 adult female mule deer from July 2012 to November 2014, equipping the deer with Iridium satellite collars manufactured by Lotek. The data was collected from the interstate Carson River herd, where a portion of the population spends the summer months in the Sierra range of California and the winter months in western Nevada. An additional 57 deer were collared in Nevada and provided by Cody Schroeder of the Nevada Department of Wildlife. Summer range is mostly within Alpine County, California, but also extends into El Dorado County and Mono County. Winter range is confined to the California-Nevada border area in Alpine County, CA. and Douglas County, NV. GPS location data was collected between February 2012 to July 2019. Between 2 and 12 location fixes were recorded per day, with a maximum of a fix taken every 2 hours during migration sequences. 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 deer 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 winter ranges and the identification and prioritization of migration corridors in a single deer population. Brownian Bridge Movement Models (BBMMs; Sawyer et al. 2009) were constructed with GPS collar data from 45 deer, including location, date, time, and average location error as inputs in Migration Mapper. Due to the large study area and a concentration of deer movement east of Lake Tahoe in the Carson Range, the population was split into two distinct sub-herds. Twenty deer contributing 52 migration sequences were used in the modeling analysis for the Carson Range. Twenty-five deer contributing 58 migration sequences were used from the rest of the population surrounding the Carson Valley. Corridors and stopovers were prioritized based on the number of animals moving through a particular area. BBMMs were produced at a spatial resolution of 50 m using a sequential fix interval of less than 27 hours. Winter range analyses were based on data from 48 individual deer and 92 wintering sequences using a fixed motion variance of 1000. Winter range designations for this herd would likely expand with a larger sample, filling in some of the gaps between winter range polygons in the map. Large water bodies were clipped from the final outputs. Corridors are visualized based on deer use per cell, with greater than or equal to 1 deer, greater than or equal to 2 deer (10% of the sample), and greater than or equal to 4 deer (20% of the sample) from the Carson Range dataset and greater than or equal to 1 deer, greater than or equal to 3 deer (10% of the sample), and greater than or equal to 5 deer (20% of the sample) from the Carson Valley dataset representing migration corridors, moderate use, and high use corridors, respectively. Stopovers were calculated as the top 10 percent of the population level utilization distribution during migrations and can be interpreted as high use areas. Winter range is visualized as the 50thpercentile contour of the winter range utilization distribution.