may seem like minor fluctuation becomes magnified upon 

 long-term application of the principles derived from the 

 simple models. Therefore, the simplified models may work for 

 almost no populations. This is particularly true for ungulate 

 populations in arid, semi-arid, or mountainous regions of 

 North America. 



Underlying assumptions of fixed forage resources 

 influenced mainly by the herbivores and density-dependent 

 dynamics resulted in the "principles" of compensatory 

 mortality and reproduction. Under this view, reducing the 

 herbivore population below the level of maximal use of forage 

 resources would result in better survival and production by 

 those remaining. The extreme degree to which the "principles" 

 of compensatory mortality and reproduction, 

 density-dependence, and a fixed forage base were carried is 

 indicated by Dasmann (1971) who stated that at the maximum 

 level (ecological carrying capacity or subsistence density) , 

 "one deer must die to make room for another". 



Often, forage resources during winter was considered to 

 be the main limiting factor. For example, Leopold (1966), 

 wrote "The quality and quantity of forage available to a deer 

 population during the most critical season of the year has 

 proven repeatedly to be the basic regulator of population 

 level. Usually this means winter forage, but not always." 



The importance of the concepts of forage carrying 

 capacity and especially winter range carrying capacity are 

 illustrated in a typical example (Fig 1.3, Cole 1961) of the 

 way the theory of density-dependent population dynamics and 

 the "principles" of compensatory mortality and reproduction 

 were applied to management of ungulates. Although this 

 management model is simplified, it was essentially the program 

 implemented throughout the United States . Deer needed to be 

 reduced below the "carrying capacity" of their range by 

 hunting. This reduction would result in greater quantity and 

 quality of food for the survivors, thereby increasing their 

 productivity. The reduction of deer numbers below "carrying 

 capacity" would allow the vegetation to "recover", thus 

 actually increasing "carrying capacity". 



For many years, there was no indication that this model 

 was working. However, this was generally attributed to the 

 belief that adequate harvests had not been achieved or that 

 vegetation took a long time to recover following 

 overpopulation by ungulates (lag effects). Although the model 

 did not appear to be working on many areas, it continued to be 

 widely applied over a broad spectrum of habitats (see 

 McCullough 1979: p. 169), perhaps because no suitable 

 alternative was proposed. 



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