Natural selection among individuals and evolutionary 

 changes in a population are important concepts in self 

 regulation theories. As population numbers rise during 

 favorable periods, more individuals of "lower quality" or 

 viability survive. Thus, the effect of weather can be 

 "density-dependent", being more severe at high populations 

 with more "low quality" individuals. 



Because the genetic composition of a population can vary 

 over time and with conditions, the "self-regulation" process 

 could work through a genetic feedback mechanism (Pimentel 

 1961). Variations on the intrinsic (self-regulation) school 

 of thought include the effects of: 1.) behavior, e.g. 

 territoriality (Wynne-Edwards 1965); 2.) physiological change 

 resulting from stress at high densities (Christian and Davis 

 1964); and 3.) the Chitty Hypothesis (Chitty 1967, Krebs 1978) 

 that population regulation can result from genetic-based 

 changes in spacing behavior. 



Although theories and variations of theories on 

 population regulation have come and gone, most widely held 

 views include the major theses of Nicholson (1933) and Smith 

 (1935). These imply a "balance of nature" and that factors 

 controlling populations, whether intrinsic or extrinsic, act 

 in a density-dependent manner. 



Population Regulation in Ungulates 



Until recently, most theoretical and empirical work on 

 population dynamics and regulation was confined to insects, 

 fish, small mammals, and to some extent birds. However, the 

 major "principles" derived were believed general and applied 

 in practice to ungulates. It was only during the mid-to-late 

 1970s that results of long-term studies on large mammals began 

 to appear (Laws et al . 1975, Sinclair 1977, Peterson 1977, 

 McCullough 1979, Botkin et al . 1981). Although these studies 

 have raised many questions and stimulated discussion, they 

 have not resulted in major new theories of population 

 regulation. 



Peek (1980) summarized current thinking on natural 

 regulation of ungulates as reflecting 1 of 2 perspectives; an 

 ungulate-habitat interaction and a predator-ungulate 

 interaction. The ungulate-habitat interaction model is most 

 widely held and applied. It is essentially Nicholsonian in 

 that density-dependent intraspecif ic competition for resources 

 is the main regulating factor. Especially for North American 

 deer (Davis 1950, Lack 1954, Dasmann 1971), this came to mean 

 that they were forage-limited. It was long believed that deer 

 were not territorial (Smith 1976, Coblentz 1977, Peek 1980), 

 nor did they have any other intrinsic mechanisms of control. 

 Thus, in the absence of predators, they were inherently 



