REMOTE SENSING OF TERRAIN SUITABILITY FOR LAMBING OF DALL'S SHEEP 
DEMPSTER HIGHWAY CORRIDOR, YUKON 
Donna L. Stewart* 
Faculty of Environmental Design 
University of Calgary 
Calgary, Alberta, Canada T2N 1N4 
ABSTRACT 
True colour aerial photography (1:50,000) of two known sheep ranges was 
analysed for potential lambing habitat. Black and white photography 
(1:24,000) was also available for one range. Two known lambing areas 
were examined and compared with 35 possible sites in the Ogilvie 
Mountains. Considered necessary for lambing are the presence of rugged, 
broken cliffs, particular elevations, slopes and aspects, vegetative 
cover and the presence of winter range nearby. The availability and 
quality of these characteristics were analysed and rated good, adequate, 
poor or uncertain. The quality of possible sites was more easily 
estimated using both colour and black and white photos. Colour analysis 
was especially useful for defining the quality of vegetative cover. Of 
the 35 sites, 5 had some of the necessary characteristics, and one was 
considered prime lambing habitat, whereas the two sites known to be used 
were interpreted as prime. It was concluded that the best possible 
habitat is presently used and the other sites analysed are clearly 
inferior. Airphoto analysis was thus found to be extremely useful in 
identifying and evaluating potential lambing habitat. It is an economic 
way to to screen potential sites and thereby increase the efficiency of 
the field work. The speed, economy and accuracy of airphoto interpreta 
tion should prove valuable in preparing environmental impact assessments 
INTRODUCTION 
Recent interest in developing non-renewable resources in northern Canada 
has raised the question of how to assess the impact of human activities 
on remote wildlife populations. The Dempster Highway provides access to 
the Beaufort Sea and passes through an area that has seen little human 
activity. As use of the highway and the corridor increases, the 
wildlife populations in close proximity to it may be affected. Critical 
areas, such as mineral licks, lambing areas and winter ranges are of 
particular concern. The identification of these areas of habitat is a 
time-consuming and costly exercise, involving many hours of flight and 
ground work. This paper explores airphoto interpretation as a tool to 
make the initial identification of possible lambing areas and to make a 
reasonable estimate of the possibility of their use. 
Dali's sheep (Ovis dalli dalli) occupy habitat in the rugged terrain of 
the Ogilvie Mountains. The Dempster Highway crossed their range and 
known lambing areas are located adjacent to it. There are actually two 
populations, one in the south Ogilvies and one in the central Ogilvies. 
Since two lambing areas were known in the south and none known in the 
central Ogilvies, this paper explores the following: 
1) Is it possible to differentiate between areas suitable and 
unsuitable for lambing? 
2) Can lambing areas be identified for the central range? 
*Present address: Public Works Canada, 1166 Alberni Street, Vancouver, 
British Columbia, Canada. 
513