Donovan, V. M., Roberts, C. P., Wonkka, C. L., Beck, J. L., Popp, J. N., Allen, C. R., & Twidwell, D. (2020). Range-wide monitoring of population trends for Rocky Mountain bighorn sheep. Biological Conservation, 248, 108639.
Species conservation requires monitoring and management that extends beyond the local population, yet studies evaluating population trends and management outcomes across the spatial range of a species remain rare. We conducted the first range-wide assessment of population trends for the iconic Rocky Mountain bighorn sheep (Ovis canadensis canadensis) of North America to investigate links between population trends and translocation history. Millions of US dollars have been spent translocating bighorn sheep to achieve conservation objectives, yet a range-wide assessment is lacking. We collected bighorn sheep population estimates for 217 populations across ten US states and two Canadian provinces. We categorized each population by translocation status: native (populations received no translocations), augmented (native populations supplemented with translocation), or reintroduced (populations beginning from translocation). Fifty-eight percent of populations increased in recent years. While most reintroduced and native populations increased in the last 5 years of records, almost double the number of augmented populations declined compared to increased. Reintroduced and augmented populations from the north-central portion of bighorn sheep range declined the most in the last 5 years of records, while southern populations tended to be more stable. Although Rocky Mountain bighorn sheep appear to be a conservation and restoration success, the threat of local population loss remains high in certain regions. We show how amalgamating multi-jurisdictional population data can assist in determining wildlife status and assessing broad-scale management outcomes.