departure from the explicit or implicit assumptions in 

 density-dependent theory that the number of animals grazing or 

 browsing is a primary factor influencing forage production and 

 quality. 



The influence of weather on vegetation production also 

 influenced cover for deer and forage and cover for alternate 

 prey (microtines and rabbits), thereby influencing coyote 

 predation rates and deer mortality. Predation rates were also 

 influenced by variable snow and ice conditions. Weather also 

 influenced the energy balance equation of deer both through 

 forage production, quality, and availability and through its 

 influence on energy demand by deer. 



Through interaction with the fixed habitat base, weather 

 (wind, snow depth, forage quantity and quality) affected the 

 kinds (reproductive, non-reproductive, long-term, temporary) 

 and amounts of effective deer habitat (space). Deep, drifted 

 snow resulted in some areas becoming non-habitat 

 (nutritionally, excessive energy use, vulnerability to 

 predation) during some winters. Similarly, during drought, 

 some areas could not provide even maintenance quality forage, 

 or their use required behavioral changes in deer that 

 increased their vulnerability to predation. 



Because of the pattern of deer dispersion at habitat 

 fill, more deer occupied marginal areas at high than at low 

 densities. Thus, mortality could be high at high densities 

 (density-related) under certain weather conditions. However, 

 this relationship was not deterministic or consistent. When 

 weather conditions remained favorable, mortality was low even 

 at high densities. 



Overall, the variable weather, interacting with the fixed 

 habitat base was the most important factor influencing the 

 deer population. This occurred because weather also 

 influenced all other factors including food, energy demand, 

 predation, available habitat (space), and even hunter harvest. 

 Within limits of the fixed habitat base, population growth was 

 limited by the time that weather conditions were favorable and 

 population decline was limited by the length of time that 

 weather conditions were unfavorable. 



The role and importance to population dynamics of 

 proximate factors such as predation and hunter harvests has 

 been discussed earlier (Chapters 5, 6, and 11). Coyote 

 predation was the major proximal cause of deer mortality. 

 Although, it appeared that predation often functioned as an 

 agent of variable weather, the absence of predators would 

 probably result in at least temporarily higher deer densities. 

 At these higher densities, it is possible that density- 

 dependent effects on reproduction and mortality might be more 



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