available information indicated that deer were in average or 

 better condition during those years. 



We conclude that in most years, fawn survival is directly 

 related to forage quality as determined by the length of time 

 plants remain green and succulent, providing quality forage 

 for lactation. Four of the 6 years excepted may be explained 

 by cycles of fat storage and depletion. If fat reserves are 

 high, females may be able to produce and nurse fawns 

 successfully, despite poor quality current forage. On the 

 other hand, a female coming out of winter in extremely poor 

 condition, with a loss of muscle tissue as well as fat, may 

 lose her fawn in utero and/or not have recovered enough to 

 successfully rear a fawn, despite good forage conditions 

 during summer. 



The assumption inherent in regressions of fawn survival 

 against estimates of forage production is that improved forage 

 conditions result in improved physical condition of deer and, 

 in turn, higher fawn production and survival. Studies of 

 captive deer document that improved nutrition results in 

 improved deer condition and improved fawn production and 

 survival (Verme 1962, 1965, 1969; and Robinette et al . 1973). 

 French et al . (1956), Robinette et al . (1973), and Rasmussen 

 (1985) further suggested that antler characteristics of 

 yearling males were sensitive to nutritional conditions. 



Because we collected data on antler characteristics of 

 yearling males relatively consistently, we were able to 

 regress those data against annual forage production estimates. 

 All antler characteristics and measurements of yearling male 

 mule deer were positively related to forb production (Table 

 5.7), which should indicate that deer condition improved with 

 increased forage production and quality. As with previous 

 regressions of fawn survival on forage production, antler size 

 (if it was related to forage quantity) should be 

 better-related to forage per capita than just relative annual 

 forage production. Antler measurements regressed against an 

 index of forage per capita also indicated significant 

 relationships, but rather than improving the relationship, the 

 inclusion of a deer density factor weakened the relationship 

 (Table 5.7). Because of that, we believe the relationship of 

 antler size with forage production estimates was not with 

 forage quantity, but with coincident forage quality. 



Trends in fawn survival and antler characteristics of 

 yearling males coincided during most years (Fig. 5.7). This 

 relationship was especially apparent during 1960-1964 and 

 1977-1986, underscoring the general relationship between fawn 

 survival, deer condition, and forage conditions. Even the 

 exceptions tended to verify the expectation that antler size 

 and deer condition were related to forage conditions . Fawn 



136 



