100 

 90 

 <5 80 

 I 70- 



^ 60- 



1 50 

 O 



2 40 



c 



LL 



* 20 



10-1 



1984-85 



1983-84 



% 

 1975-76 



1971-72 



1964-65 



1981-82 1968-69 





• • 



1978-79 



0.0 



10.0 20.0 



Winter Severity Index 



30.0 



Figure 5.14 



A plot of mule deer fawn mortality during 

 winter against a winter severity index. 



average during both 1961 and 1962. Thus, high fawn mortality 

 during winter 1964-65 occurred when forage conditions had been 

 poor for 3 of the 4 prior summers and deer were probably in 

 relatively poor condition entering winter. 



The winter of 1968-69 was very severe; the severity index 

 was higher during only 3 other winters . Number of deer 

 entering winter was at the long-term average and fawn 

 mortality was moderately high, though not catastrophic. 

 Forage conditions had been above average for 3 of the 4 prior 

 summers (Fig. 3.9), and accumulated fat reserves probably 

 enabled the deer population to get through winter without 

 catastrophic mortality. 



147 



