182 



activity in spring and summer with the building up of fat 

 reserves. The timing of the aerial surveys also affects the 

 activity observations. Aerial surveys were started at sunrise 

 in spring, summer, and fall, coinciding with high feeding 

 activity. The winter surveys were conducted later in the day, 

 when deer are more apt to be bedded or inactive. 



Table 96. Seasonal activity of mule deer in the Birney study area. 



Activity 



Spring 

 1980 



i 



Summer 

 1980 



Fall 

 1980 

 % 



Winter 

 80-81 

 % 



Spring 

 1981 



Summer 

 1981 

 % 



\ 



Use of Topography: The percentage of mule deer observed on mesa- 

 butte tops was highest during the summer 198O and winter 198O-81, 

 but was substantial during other seasons (Table 97). The lack 

 of good riparian cover at lower elevations, and the very hot, dry 

 weather may have caused the shift to higher elevations during the 

 summer of I98O. During winter, 90^ of the mule deer were observed 

 on mesa-butte tops or steep side slopes, reflecting the location 

 of their winter range. High percentages of mule deer were observed 

 on dissected mid-slopes during spring and summer. Use of alluvium/ 

 terrace and current flood plain areas was highest during fall, 

 reflecting the fall movement of mule deer down to the Tongue River. 



Use of exposure : Use of flat areas (no exposure) was substantial 

 during all seasons of the study, reflecting the high use of mesa- 

 butte tops (especially in winter) and river bottoms in fall 

 (Table 98). East and northeast exposures received heavy use 

 during spring and summer. A total of 19/5 of the mule deer were 

 observed on north, northeast, and northwest facing slopes during 

 winter. This percentage probably would be lower during a normal 

 winter. 



Use of slope; The highest percentage of mule deer observed on 

 steep side slopes was in winter (Table 99). This correlates with 

 the high use of mesa-butte steep side slopes at this time of 

 vear. More deer were observed on steep side slopes in 1981 

 than in 1980. Low rainfall in 1980 probably resulted in poor 

 browse conditions on the sparsely vegetated steep slopes. Medium 

 slopes supported 1/3 to 1/2 the deer observations, except in winter. 

 Use of gentle slopes was highest during soring 198O, reflecting the 

 high use of gently sloping sagebrush flats. 



