Mule Deer Stone Hills Migration Map and Statistics

This analysis uses location data collected on mule deer that were fitted with GPS collars in Idaho for 2003 – 2019. Individuals using a winter range (as defined as a winter herd), were used for the analysis if their location data was available at the time of the analysis. Each individual’s location dataset is used to estimate winter and summer ranges, and seasonal spring and fall migration using net-squared displacement techniques (Bunnefeld et al. 2011). Fall and spring migration locations are used for the migration route analysis. After individual mule deer spring and fall migration locations are determined, a Brownian Bridge Movement Model (BBMM, Horne et al. 2007) is used to estimate the individuals Utilized Distribution (UD) during the seasonal migrations. Depending of the frequency of the location data, either a BBMM or a Forced Motion Variance model (FMV) are used as an estimate of that season’s migration UD. If locations collected at a lt 7hr schedule, the migration used BBMM modeling techniques. If the schedule was greater than 7 hrs a FMV modeling technique was used (Fatteberge et al, in review). Further, FMV techniques that allowed for a 14 hour gap in location schedule were preferred over FMV models that used a maximum of 27 hr gap. When an individual had several seasonal migrations, the resulting UDs distributions are combined and averaged to create a single UD of all the seasonal migrations conducted by that individual. Individual UDS are then combined for all individuals in the winter herd with available UD information. For migration routes, the following classes were delineated based on the area’s use across the winter herd, used by 1 individual, used by 2individuals to 10% of the winter herd, 10 to 20% use of the winter herd, and greater than 20% use by the winter herd. Migration routes used only by 1 individual are then omitted from the analysis. The combined individual UDS are aggregated to estimate winter herd stopover locations. From the combined winter herd UD, the top 10% of recorded values are selected to represent population level stopovers. Winter herd stopovers that occurred on single use migration routes are omitted from the analysis. *** The Stone Hills mule deer seasonal migration analysis is limited by the number individuals such that only 10 to 20%, and greater than 20% migration route use could be classified. It is likely that IDFG will update mapped migration routes as additional spatial and temporal data becomes available. Stone Hills Mule Deer Migration Statistics Analyzed/Prepared by: Jodi Berg & Scott Bergen July 2021 Spatial Metrics Average length of Migration: 25.9 miles Maximum Migration Length: 37.3 miles Minimum Migration Length: 11.1 miles Total Migrations Analyzed: 31 Total Number of Individuals: 19 Total Number Spring Migrations: 23 Total Number Fall Migrations: 8 Of 31 individual seasonal migrations, 12 used Brownian bridge movement models with an 8-hour time-lag, 17 used forced motion variance (1000 m) models with a 14-hour time-lag, and 2 used forced motion variance (1000 m) models with a 27-hour time-lag. Temporal Data Extent of Study: April 14, 2017 – April 29, 2021 Spring Migration Fall Migration Start Date Average March 29 November 28 Minimum January 18 October 18 Maximum April 30 December 2 End Date Average April 23 December 15 Minimum April 5 November 8 Maximum May 10 January 19 Duration Average 21 21 Minimum 2 12 Maximum 42 29 Migration Use Class Statistics Use Class Acres 1 individual 176,777 Low (>2 individuals) -- Medium (10-20%) 76,186 High (>20%) 23,554 Stopover 10,066 Use Class (REVISED) Acres Low (>2 individuals) -- Medium (10-20%) 75,709 High (>20%) 23,554 Stopover 9,196