Trout Creek-Big Creek Elk Migration Maps and Statistics

This analysis uses location data collected on elk that were fitted with GPS collars in Idaho for 2007 – 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 elk 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 less than 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. 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. Trout and Big Creeks Elk Migration Statistics Analyzed/Prepared by: Jodi Berg and Scott Bergen May 2021 Spatial Metrics Average length of Migration: 8.8 miles Maximum Migration Length: 54.1 miles Minimum Migration Length: 1.8 miles Total Migrations Analyzed: 68 Total Number of Individuals: 31 Total Number Spring Migrations: 44 Total Number Fall Migrations: 24 Of 68 individual seasonal migrations, none used Brownian bridge movement models with an 8-hour time-lag, 46 used forced motion variance (1400 m) models with a 14-hour time-lag, and 22 used forced motion variance (1400 m) models with a 27-hour time-lag. Temporal Data Extent of Study: March 7, 2015 – November 2, 2019 Spring Migration Fall Migration Start Date Average April 25 November 30 Minimum February 20 July 23 Maximum August 2 January 24 End Date Average May 12 December 23 Minimum March 5 August 18 Maximum September 2 February 9 Duration Average 16 17 Minimum 3 3 Maximum 86 81 Migration Use Class Statistics Use Class Acres 1 individual 181,107 Low (>2 individuals) 84,954 Medium (10-20%) 39,852 High (>20%) 12,976 Stopover 10,026