these variables, mean temperature during May explained 67% of 

 the variation in fawn survival and July-April precipitation an 

 additional 14%. Because forage per capita was not closely 

 related to fawn survival, the relationship of mean May 

 temperature to fawn survival probably was a reflection of the 

 relationship between spring temperature and phenological 

 development of f orbs . High survival of fawns was related to 

 cool spring temperatures, which resulted in slower plant 

 development and a longer period of quality forage. 



We examined residuals of the regression of July-April 

 precipitation and mean May temperature on fawn survival to 

 December to determine why 6 of 27 years did not fit the 

 regression. The plot of residuals (Fig. 5.6) includes 

 residuals for years which did not fit the regression (1965, 

 1969, 1974, 1975, 1980, and 1984). Fawn survival was 

 significantly below expectations, based on forage factors, 

 during both 1965 and 1984. Both years followed winters during 

 which mortality was high and included adults, thus surviving 

 females may have remained in poor condition through 

 parturition and lost their fawns. Forage during those years 

 was used to replace body fat reserves and muscle tissue rather 

 than to rear fawns. 



Similar winter mortality occurred during 1971-72. 

 Although fawn survival was also lower than expected in 1972 

 (Fig. 5.6), it was not significantly lower. However, more 

 adult females died that winter than in any other and thus did 

 not survive to be recorded as barren females the next year. 

 Moreover, a higher than usual percentage of the survivors that 

 year may have been females that had not weaned a fawn the 

 previous year and were in good enough condition to rear a fawn 

 in 1972. 



Fawn survival during both 1969 and 1980 was significantly 

 above levels expected based on forage conditions. Both years 

 followed 2 years of above-average forage conditions and were 

 the third years of population increases. It is probable that 

 fat reserves were built up over the 2 previous years and fawn 

 survival was achieved on fat reserves of the females in 

 addition to current forage. 



During 1974 and 1975 (Fig. 5.6), fawn survival was 

 significantly below that expected based on forage conditions. 

 Those years followed 3 others (1971-1973) during which fawn 

 survival was below expectations, although not significantly 

 so. Both casual observations and the results of our 

 regressions indicated that poor fawn survival during the 

 early- to mid-1970s, and especially 1974 and 1975, should not 

 have been the result of poor forage conditions. Additionally, 



134 



