periods, winter mortality of adult females averaged 6.8%, 

 6.1%, and 5.4%, respectively. Averaged over long periods, 

 hunting mortality increased average annual mortality, but did 

 not result in a "compensatory" reduction in winter mortality 

 rates. A plot of natural mortality rate against hunting 

 mortality rate for individual years (Anderson and Burnham 

 1976) did not indicate decreasing natural mortality with 

 increasing hunting mortality for adult females (Fig. 11. 1A). 



These findings appeared contrary to current concepts 

 concerning compensatory mortality in deer, which hold: 1) 

 that harvest removes animals that would otherwise die from 

 another cause; and 2) that harvest removal of any animal from 

 a population increases the chance of survival (reduces 

 mortality) of remaining animals and/or those of a subsequent 

 cohort in a density-dependent manner. Because of this, it 

 seems essential to further examine both concepts as they apply 

 to mortality patterns and rates of adult females. 



It is possible that the low average natural mortality 

 rate of adult female mule deer on the area (X = 7.2% with no 

 hunting) allowed little opportunity for compensation to occur. 

 Most work supporting the concept that harvests remove animals 

 that would otherwise die has involved species populations like 

 birds that commonly experience natural mortality rates of 50% 

 or more per year. If a relatively low percentage of all adult 

 females is destined to die over winter (X = 6.2% in this 

 study) , and those most likely to die are not selected for or 

 against by hunters, only 6.2% of the hunter harvest can be 

 "compensatory" (substitute for natural loss). The remainder, 

 or more than 9 of every 10 adult females shot on the average, 

 is additive and will contribute toward a decline in the 

 population. Thus, annual survival of adult females declined 

 in an almost straight line with hunting mortality rate (Fig. 

 11. IB) . 



Overwinter mortality rates may vary considerably 

 (0.7-24.8% during 1960-1986), however, such that the exact 

 degree to which harvest losses in any given year may 

 substitute (be "compensatory") or be additive will also vary. 

 It also may depend on a number of other variables, including 

 the age structure of the adult female segment of the 

 population. The apparent higher harvest rate for older (8.5 

 +) females than younger females may indicate a slightly 

 greater average degree of substitution than 6.2% for that 

 segment or for the female population in years when animals in 

 that age group are relatively common. Somewhat greater than 

 average compensation could also occur when emigration of 

 yearling females during some years is taken into account. 

 Vacant home ranges of some harvested adult females could be 

 occupied by yearling females which might otherwise have left 

 the population. 



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