Dall Sheep in Denali

NPS Photo / Lian Law

Figure 1: Ratio of lambs per 100 ewes and yearlings in Denali National Park and Preserve, 2009-2014

Aerial Survey

No formal aerial surveys were conducted in Denali in 2014. The most recent extensive survey, in 2011, estimated a population of 2,321 sheep in areas north of the Alaska Range continental divide. Plans are currently being developed to repeat this survey during July 2015.

Ground-based Surveys

From 2008 to 2014, park staff conducted annual ground-based Dall’s sheep surveys. Ground surveys allow closer and more careful observation of sheep and provide detailed and accurate herd composition data, but the areas that can be surveyed on foot are very limited. Although these data are useful as an indicator of changes from year-to-year, the results may not be applicable to the entire sheep population in Denali.

Denali staff conducted ground-based Dall’s sheep surveys during June 6-10, 2014. These surveys classified sheep as lambs, ewes, yearlings, or rams (whenever possible, rams were also classified by horn size). The lamb productivity estimate was 15 lambs per 100 ewes and yearlings. This was greater than estimates from the previous 2 years, but still quite low compared to stable or increasing sheep populations (which generally exceed 20 lambs:100 ewes and yearlings). Since 2009, sheep productivity in Denali has ranged from 3-34 lambs per 100 ewes (Figure 1).