Aerial Survey of Dall’s Sheep: Yukon-Charley Rivers National Preserve, July 2015.

摘要

Dall’s sheep (Ovis dalli) inhabit the mountains and river bluffs of Yukon-Charley Rivers National Preserve (YUCH) at low density. Hunting, both sport and subsistence, of sheep is allowed in the Preserve. Since 1993, the sport hunt has been “open” (i.e., it is not limited to a certain amount of drawing permit holders). Sheep surveys in the YUCH area started as early as 1973 (Burch 2010). Since 1997, aerial sheep surveys in YUCH have focused on 7 units (Figure 1; 5580 Mountain, Charley River Bluffs, Cirque Lake, Copper Mountain, Diamond Fork Mountain, Mount Sorenson and Twin Mountain). Major declines in sheep populations from across Alaska in 2013 and 2014, and the fact that the sheep population had not been surveyed since 2009 helped prompt this project. Minimum count surveys have been used to monitor this population. Newer techniques, such as distance sampling (Schmidt et al. 2012), may not be appropriate for surveying YUCH sheep as the population size and density is relatively low, with relatively few groups of sheep.