Dall’s sheep survey within Yukon-Charley Rivers National Preserve: July 2023
Sorum M. 2024. Dall’s sheep survey within Yukon-Charley Rivers National Preserve: July 2023. Science Report. NPS/SR—2024/120. National Park Service. Fort Collins, Colorado. https://doi.org/10.36967/2303340
A minimum count survey of Dall’s sheep (Ovis dalli) in Yukon-Charley Rivers National Preserve was conducted from July 18 to 20, 2023. The Preserve was last surveyed in July of 2018. The current survey examined the same 7 core survey units as the previous survey and the Ogilvie Mountains. In the core area (the 7 units most often surveyed), 70 sheep (32 ewes, 13 lambs, 6 yearlings and 19 rams) were detected. This constitutes a 75% decrease from the long-term average (284 sheep, 1997–2018) and a 68% decrease from the last survey (221 sheep, 2018). There were 40 lambs, 19 yearlings, and 59 rams per 100 ewes in the core area. Declines varied by space and sex classes. Declines were greater in survey units with historically fewer sheep and lower proportions of ewes (91% decline; 5580 Mountain, Copper Mountain, Diamond Fork, Twin Mountain) versus the survey units with more sheep and higher proportions of ewes (67% decline; Charley River, Cirque Lakes, Mount Sorenson). Across the latter more populous survey units, ewes and rams declined by 70% and 40%, respectively, compared to the long-term average. For the first time, no sheep were observed in two of the survey units (Copper Mountain and Diamond Fork). In the Ogilvie Mountains, 26 sheep were detected (18 ewes, 4 lambs, 0 yearling and 4 rams) representing a 28% decline since the last survey. This translates to 22 lambs, 0 yearlings and 22 rams per 100 ewes.
- Type
- Published Report
- Authors
- Sorum, Mathew
- Date of Issue
- 2024-05
- Publisher
- National Park Service
- DOI
- 10.36967/2303340
- Units
- NRSS , YUCH