Space use and movement patterns of translocated bighorn sheep

Abstract

Ungulate species have consistently been a major focus of reintroductions to their native ranges. Bighorn sheep (Ovis canadensis) are an ecologically sensitive species, and have experienced population declines throughout their historic range; bighorn sheep inhabited the Black Hills region of South Dakota but were extirpated from the area due to anthropogenic impacts in the early 1900s. To continue to restore populations to the area, we translocated 26 bighorn sheep from Alberta, Canada to the Deadwood Region of the Black Hills. Bighorn sheep were fitted with VHF or GPS collars and monitored throughout the duration of the study (Feb 2015–Jan 2017). Our objectives were to evaluate movement patterns post-release of bighorn sheep in the translocated Deadwood bighorn sheep herd. We utilized 3 types of home-range analyses based on collar data; kernel density estimation (KDE), minimum convex polygon (MCP), and Brownian Bridge Movement Models (BBMM) were used to estimate home-ranges year 1, year 2, and for the duration of the study. Home-range size utilizing KDE (95%; $$\overline{x}$$ = 41.41 km2, SE = 10.50), minimum convex polygon (95%; $$\overline{x}$$ = 55.73 km2, SE = 15.04), and BBMM (95%; $$\overline{x}$$ = 32.95 km2, SE = 4.67) differed among methods. Year 1 home-range sizes (95% BBMM; $$\overline{x}$$ = 40.01 km2) were larger than year 2 (95% BBMM; $$\overline{x}$$ = 4.08 km2) home-range sizes. Travel distances were also larger in year 1 ( $$\overline{x}$$ = 431.80 km) than year 2 ( $$\overline{x}$$ = 368.77 km). Our results indicate that after an acclimation period, which included individual dispersal, the translocated Deadwood bighorn sheep herd settled into smaller home-ranges near the release site.