Effect of Cattle and Elk on Mule Deer Population Performance 



Most studies on the effects of livestock grazing on deer 

 have documented differences or overlaps in food habits, 

 distribution, and habitat use. Few, if any, have documented 

 population impacts . We have data on mule deer population 

 performance under a season-long grazing system over a long 

 period of time, and also have data to compare between season- 

 long and rest-rotation livestock grazing systems. We could 

 not detect any differences in mule deer fawn survival or 

 population trend for the 2 grazing systems. 



Mule deer population trend was the same for both grazing 

 systems during 1975-76 through 1986-87 (Figure 9.10). Any 

 differences that may have occurred were too subtle to detect 

 from our population estimates. The 2 pastures of the rest- 

 rotation system that were within "breaks" mule deer habitat 

 encompassed 202 km 2 compared to 275 km 2 for the season-long 

 grazing system. Mule deer density during spring ranged from 

 0.5 mule deer/km 2 to 3.4/km 2 on the rest-rotation system and 

 from 1.4/km 2 to 4.5/km 2 on the season-long grazing system. We 

 believe those differences were related to habitat structure 

 and composition rather than grazing systems. 



1500n 



o 

 o 

 q 1000 



0) 



0) 

 -O 



E 



500- 



-• Continuous Grazing April - November 



-o Rest-rotation Grazing System NCRCA 



1976 1978 1980 1982 



Year 



1984 



1986 



Figure 9.10 



Spring mule deer population trend within a 

 season-long and a rest-rotation grazing system, 

 1976-1987. 



271 



