Monthly mule deer winter density indices obtained during aerial census 

 were averaged for each section in the Mine Study Area for the winter of 

 1979-1980 and for all four winters since 1976. These data were used to 

 create density index isopleths which show general patterns of winter dis- 

 tribution (figures 9 and 10). Both figures show that deer tend to con- 

 centrate in areas of coulee and badlands topography in the northwest, 

 southwest, and southeast 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 approximately one kilometer.) 



White-tailed Deer . Only 28 observations of white-tailed deer were 

 recorded during the report period (table 7). Groups of up to five white- 

 tailed deer were seen in the north-central portion of the Mine Study Area 

 (sections 25, 29, 30, 31, and 32) in May, June, July, August, and October. 

 A single observation was made near the sagebrush census plot in July. 



Pronghorn . A summary of pronghorn observations during the study 

 period is presented in table 8. Production ratios during the period 

 1977-1979 (based on all July through October observations of fully classi- 

 fied groups) are shown in figure 11. A production ratio of 197 fawns/100 

 does was obtained in 1979; this is the highest obtained since the study 

 began in 1977. Results of the July, 1979, pronghorn aerial census of 

 Hunting District 650 are presented in table 9. Aerial census data 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 obtained during a single flight in the period July-October) are 

 shown in figure 12 for the period 1977-1979. These data indicate a de- 

 crease in summer- fall pronghorn density in the Mine Study Area since 1978, 

 although the Permit Area showed an increase. Winter density increased 

 markedly since the last monitoring period due to mild winter conditions 

 and lack of snow cover. 



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 and also for all years since 1976 combined. These 

 data were used to create density index isopleths which show general patterns 

 of distribution (figures 13 through 16). As indicated by these maps, 

 pronghorn are most commonly found in the southwestern, south central, and 

 northwestern portions of the Mine Study Area in summer. During the mild 

 winter encountered during the study period, pronghorn were very abundant 

 on the rolling grassland and sagebrush areas immediately southwest of the 

 Mine Study Area. Some groups ranged into the southwestern corner of the 

 Mine Study Area and into the sagebrush flats along lower Romine Coulee. 

 A few groups were seen during the ground surveys 2-4 km (3 to 6 miles) 

 northwest of the Dreyer ranch house. 



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