3)Can a reasonable estimation of expected use be made? 
STUDY AREA 
The study area was the Dempster Highway Corridor, a 16 km-wide strip 
from km 80 to km 198 (North Fork Pass to the Ogilvie River). The south 
Ogilvie sheep range is from km 80 to km 94 and the central Ogilvie range 
is from km 171 to km 198* The Ogilvie Mountains are characterized by 
rugged topography more than 1000 metres above sea level. Trees are 
limited to protected valleys below 1050 metres and discontinuous perma 
frost underlies the region. In the central Ogilvies there are unglaciated 
regions of heavily eroded, flattened hills and deeply incised river 
valleys. There are no permanent residents within the study area. 
ANALYSIS 
Materials 
Both colour and black and white photos in stereo pairs were analysed 
under 3X magnification. The colour photography was flown on August 20, 
1977 at approximately 7,000 metres above sea level, and is at a scale of 
1:50,000. Coverage was available for both sheep ranges. Black and 
white photos were available only for the central Ogilvies and are at a 
scale of 1:24,000. This photography was flown on July 25, 1978 at 
approximately 4,400 metres above sea level. Both flights were made for 
Foothills Pipe Lines (Yukon) Ltd., for planning of the Dempster Lateral 
Gas Pipeline Project. Thus the photography was centred about the 
Dempster Highway Corridor. 
Methods 
The stereo photos of the study area were examined and cliff areas in 
proximity to the highway were chosen for analysis and outlined. All 
sites were then analysed in terms of six characteristics of lambing 
areas and a suitability rating of good, adequate, poor or unknown was 
assigned to all characters at each site. 
Lambing Area Characteristics 
A lambing area consists of the actual location of birth and the forage 
area around it. The ewe removes herself from the other sheep and 
remains separate for several days after the birth. Then she and the new 
lamb rejoin other ewes, lambs and yearlings. The nursery herd remains 
close to the lambing cliffs, proceeding to summer range when the lambs 
are able to travel distances. 
Presence of Cliffs. The use of rugged, broken cliffs where protection 
from predators and weather, especially wind, is found is well documented 
(Murie 1944, Pitzman 1970, Geist 1971). To receive a "good" rating, the 
cliffs must consist of several well-separated outcrops that provide 
various options for escape for sheep foraging in open areas. Height is 
a factor and the outcrop must provide very protected, isolated areas for 
the actual birth. 
Altitude. Lambing areas are generally found at sufficient altitude 
to provide protection from predators and are windblown enough to free 
the ground of snow. Sheep may take advantage of warm temperatures caused 
by thermal inversions at mountain tops (Pitzman 1970, Nolan and Kelsall 
1977). An estimation of position relative to the valley floor and to 
the mountain peak, rather than an actual measurement, was made. Ease of 
access to predators from below and above was considered. A "good" 
*For a complete description of these populations see Stewart (1981). 
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