Table 6 represent the minimum number known to be present (i.e., 186 mule deer 

 were observed during the February flight, although there may have been more that 

 were not seen), the density indices shown in Figure 6 may be somewhat lower than 

 true densities. The data indicate a decrease in mule deer winter density in the 

 Mine Study Area since the last monitoring period; the Permit Area, however, 

 showed an increase. Densities were similar for the control area and the Permit 

 Area. 



Monthly mule deer winter density indices obtained during aerial censuses 

 were averaged for each of the 114 sections in the Mine Study Area for the winter 

 of 1980-1981 and for all winters since 1976. These data were used to create 

 density index isopleths that show general patterns of winter distribution 

 (Figures 7 and 8). Both figures show that deer tend to concentrate in areas of 

 coulee and badlands topography in the northwestern, southwestern, and 

 southeastern portions of the Mine Study Area, as well as near the Waller ranch. 

 (Since, for mapping purposes, deer were assumed to be concentrated in the center 

 of each section, distribution as indicated by the isopleths is only accurate to 

 within about 1 kilometer.) 



White-tailed Deer . Use of the Mine Study Area by white-tailed deer 

 increased markedly in 1980; 114 observations were recorded during the monitoring 

 period (Table 7), compared to only 28 in 1979. Much of this increase was due to 

 incorporating sections 21-24, which were used in fall and winter by groups of up 

 to 8 white-tailed deer, into the northeastern corner of the expanded Mine Study 

 Area. Two other important use areas were identified in the Mine Study Area. 

 Sections 29-32 just west of the Dreyer ranch house were used extensively by 

 groups of up to 8 deer. Although this area was used during all seasons, use was 

 heaviest in the fall of 1980. Groups of up to 3 deer were observed near the 

 sagebrush bird census plot close to the southwestern edge of the original 

 Proposed Mining Area (area X) in the spring, summer, and fall. Additional 

 observations were made near stockpond MAOl about 2 miles SSE of the Dreyer ranch 

 house . 



Pronghorn . A summary of pronghorn observations made during the study period 

 is presented in Table 8. Production ratios for the Mine Study Area from 1977- 

 1979 (based on all July through October observations of fully classified groups) 

 are shown in Figure 9. A production ratio of 64 fawns/100 does was obtained in 

 1980; this is the lowest ratio obtained since the study began in 1977. (NOTE: 

 1979 production was 107 fawns/100 does, not 197/100 as reported on p. 33 of the 

 second annual report.) In contrast, the 1980 production ratio in DFWP Hunting 

 District 650 was 101 fawns/ 100 does (Table 9). Results of the July 1980 

 pronghorn aerial census of Hunting District 650 are presented in Table 9. 

 Aerial census data for the Mine Study Area are presented in Table 6. Winter 

 density indices (as described under Mule Deer, above) and summer-fall density 

 indices (based on the largest aerial census figures obtained during a single 

 flight in the period from July-October) are shown in Figure 10 for 1977-1980. 

 These data indicate an increase in summer-fall pronghorn density in the Mine 

 Study Area since 1979, although densities in the Permit Area showed a decrease. 

 Winter density in the Mine Study Area increased markedly since the last 

 monitoring period due to mild winter conditions and lack of snow cover. In 

 fact, winter 1980 densities were the highest obtained since the study began in 

 1976. 



Monthly pronghorn summer and winter density indices obtained during aerial 

 censuses were averaged for each section in the Mine Study Area for the report 

 period as well as for all years since 1976 combined. These data were used to 



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