actual population levels. The estimated population levels from 

 1934 to date are illustrated by Line A, Figure 2. 



1934 through 1950 



Population observaticxis made by Ensign (1937) and Brink (1941) 

 were an accumulation of sightings by observers on foot. Sheep were 

 undoubtedly missed during these surveys, therefore, the estimates 

 are considered to be the absolute minimum population present 

 through this time period. The estimates contained in the U.S. 

 Forest Service Annual Wildlife Reports for this period correlate 

 well with the estimates contained in the reports of Ensign (1937) 

 and Brink (1941). These estimates were made when a substantial 

 amount of time was spent collecting field data from the Ural-Tweed 

 area and it was assumed the personnel making the estimates had a 

 good know]3dge of the bighorn population. The estimation of the 

 population trend through this period of time was determined by 

 plotting a curve through the points representing the realistic 

 population estimates for the area. 



1951 through 1960 



During this period only the population estimate made by Blair 

 (1955a) was considered to be reliable. The mid-point (162.5) of 

 the range (150-175 head) estiipated by Blair (1955a) was used as the 

 population level for this period. The estimates by the Montana 

 Department of Fish and Game and the U.S. Forest Service during this 

 period were considered to be over estimates (R. Weckwerth 1983, 

 pers. commun.). These estimates were made for end of the year 

 reports and were based on little or no field data. Since these 

 estimates were considered to be unrealistic, they were not used in 

 determining the overall population trend. 



1961 through 1970 



Only one population estimate for this period was located. U.S. 

 Dep. Inter. (1965) in an analysis of the potential impacts of the 

 Libby Dam project estimated there were approximately 170 bighorn 

 sheep inhabiting the Ural-Tweed range. U.S. Forest Service Annual 

 Wildlife Reports for this period were considered to be fairly unre- 

 liable, as evidenced by the excessive estimates for the 1950 's and 

 were not reviewed. 



1970 to date 



At the completion of his study. Brown (1979) estimated there 

 was a total popuJ.ation of no more than 25 sheep. In 1981, 22 sheep 

 were observed on the area. These estimates were considered to be 

 reliable indicators of the actual population level at the time of 

 the surveys. 



Harvest data from 1954 to 1974 were helpful in evaluating the 

 validity of some of the estimates. Wishart (1978) following a 



31 



