influences adult sex ratios observed on an area. Sex ratios 

 in mule deer populations across the broad spectrum of habitats 

 occupied is not always correlated with obvious mortality 

 factors such as hunting that impact males more than females. 

 There are, for instance, mule deer populations that experience 

 much lighter hunting pressure than deer on our study area but 

 maintain much lower adult male: female ratios. 



During summer and early autumn, distribution and habitat 

 use of mature males was significantly different from that of 

 females and fawns. Females and fawns occupied sites and 

 habitats that were more diverse, with better forage and cover 

 components than areas occupied by mature males. Significant 

 differences in habitat use were not apparent during late 

 autumn and early winter. It appeared that the aggressive 

 behavior and dominance of parturient females during late 

 spring and early summer determined home range location and 

 distribution for all deer. Parturient females appropriated 

 optimal fawn-rearing habitat and other deer, including 

 non-productive females, yearling males, and mature males 

 generally had fit in to any areas not occupied by productive 

 females. Those areas may be adequate to support non-lactating 

 adult deer, but will not, at least consistently, support 

 lactating females. Yearling deer must establish in areas 

 where there are no deer or where they are tolerated by 

 existing deer. In some areas and some years, that can mean 

 emigrating from the population. 



For purposes of illustrating our hypothesis, we assume 

 that 4 categories of habitat occur: 1) optimal fawn-rearing 

 habitat, 2) sub-optimal habitat, allowing adult survival, but 

 not fawn survival during some years, 3) marginal habitat, 

 where adults may survive with specialized habitat use and 

 movements, but few, if any, fawns are recruited, and 4) non- 

 or only transiental deer habitat. Adult sex ratio may be at 

 least partially determined by the relative proportions of 

 these 4 types of habitat within the area surveyed. Relatively 

 high proportions of sub-optimal and especially marginal 

 habitats may be necessary for an area to support many adult 

 males. There are some areas that contain habitat that support 

 recruitment of fawns and everything else around it is non-deer 

 habitat. Tentative indications are that these areas generally 

 have low adult male: female ratios. The adult males could 

 certainly live and survive in the fawn-rearing habitat, but 

 few find places to live that are not occupied by agonistic 

 females during the fawn-rearing period; thus most males must 

 emigrate to other areas, out of the population. 



Sub-optimal and marginal areas also provide less habitat 

 that will support deer during the most extreme conditions such 

 as drought and severe winters. As the population increases 

 during years or periods of years of good conditions for fawn 



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