The longer the relative reproductive life span, the more 

 likely "reproductive restraint" becomes adaptive. 



Population theorists, beginning with Malthus and Darwin, 

 traditionally have looked at the impressive reproductive 

 potential of most populations and concentrated their efforts 

 on the role and importance of mortality in population 

 regulation. This view forms the basis for much current 

 population theory. In harsh, variable, and unpredictable 

 environments, however, it may be equally valid to assert that 

 high reproductive potential is necessary to cope with inherent 

 regular or periodically high mortality (Fisher 1930, White 

 1978). Although changes in reproductive rates, by themselves, 

 were not sufficient to significantly regulate population 

 growth of deer on our study area, reduced reproductive rates 

 usually coincided with high fawn mortality after birth; they 

 often coincided with increased adult mortality as well. If 

 reduced reproductive rates and high post-partum mortality 

 rates often resulted from the same ultimate factor(s), 

 variations in the operation of such factor or factors may 

 explain much of the variation in deer numbers. 



Variation in Mortality Rate 



The relative intensity of operation or relaxation of 

 factors affecting mortality rates of fawns and adults appeared 

 to exercise the greatest impact on population growth rates and 

 trends. It should be noted, however, that from the standpoint 

 of population dynamics and regulation, the role and impact of 

 fawn mortality differed from that of adult mortality. Factors 

 affecting fawn mortality determined annual recruitment to the 

 adult segments of the population, whereas those affecting 

 adult mortality determined losses. Also, the relative 

 importance of various mortality factors differed between fawns 

 and adults. This, plus the fact that our data indicated 

 recruitment to the reproductive population was not effectively 

 achieved until individuals were at least 1 year old, required 

 that mortality rates and causes for fawns and adults be 

 addressed separately. 



Fawn Mortality 



Annual mortality rate of fawns varied considerably among 

 years (17-94%) and population trend generally followed the 

 trend in fawn mortality by 1 year. Most mortality occurred 

 during summer ( ave . 65%), but seasonal rates varied widely 

 among years . 



Predation by coyotes was the single most important 

 mortality factor for fawns, accounting for 88% of all deaths 

 of radio collared fawns and 85% of deaths in summer and 

 autumn. Overall, coyote predation on fawns was generally 



294 



