Application of the density-dependent harvest model in 

 deer management during the 1940s to early 1960s did not appear 

 to increase deer productivity, but initially no problems 

 developed as a result of its use. During the late 1960s and 

 early 1970s, however, a widespread decline in mule deer 

 populations across western North America occurred "despite" 

 continued heavy harvest and "recovering" vegetation on many 

 areas. Existing concepts and principles of deer management 

 could not explain the decline (Workman and Low 1976). 



Inadequacy of Existing Concepts 



Prior to and during the time mule deer populations in 

 western North America apparently collapsed, other scientists 

 were questioning the generally accepted theories of population 

 regulation. Thus, although density-dependent regulation had 

 been assumed to be a reality, Lack (1966) indicated that long- 

 term studies of birds failed to adequately demonstrate 

 empirical evidence for density-dependent regulating 

 mechanisms. He, like many others, was forced to defend 

 density-dependent regulation as a "logical necessity". 

 Similarly, Watson and Moss (1970) wrote: "Clearly, density- 

 dependence and equilibrium levels are statistical concepts, 

 not necessarily biological reality." Ehrlich and Birch (1967) 

 questioned the concept of a "balance of nature" and the 

 overriding importance of density-dependent population 

 regulation. Birch (1971) continued to emphasize the 

 importance of environmental and genetical heterogeneity in 

 population regulation. 



From a mathematical and statistical perspective, Maelzer 

 (1970) and St. Amant (1970) showed that regression analysis 

 previously used to "prove" or detect density-dependent 

 regulation did not necessarily do so. Random variation could 

 give the same results as density-dependent regulation when the 

 often used technique of regressing log population density 

 against log previous population density was employed. Thus, 

 the relationships between population density and growth rate 

 as proposed by Tanner (1966) were also subject to question. 



If the concept of density-dependent population regulation 

 was questionable, at least in some areas or for some 

 populations, then harvesting theory based on that concept 

 would also be questionable. The "unexplained" decline of mule 

 deer on our study area and elsewhere during the early to mid 

 1970s led us and others to question these concepts as they 

 related to mule deer in much of Montana. 



In concluding this review of past studies, theories, and 

 problems, we note that most data collected or analyzed to 

 form, "prove", or verify prior theories of population 

 regulation came from short-term studies, introduced or 

 founding populations, and laboratory, penned, or island 



14 



