Endocrine Adaptive Mechanisms 

 and the Physiologic Regulation 

 of Population Growth* 



J. J. CHRISTIAN V^^ 



Division of Endocrinology and Reproduction, Research Laboratories, 

 Albert Einstein Medical Center {North), Philadelphia, Pennsylvania 



General Introduction 189 



Part 1. The Endocrine Adaptive Mechanisms 191 



I. Introduction 191 



II. The Endocrine Glands of Adaptation 192 



A. The Adrenal Glands 192 



B. The Thyroid Gland 228 



C. Other Endocrine Adaptive Factors 240 



D. General Measurements of the Endocrine Adaptive Responses 242 



Part 2. Physiologic Adaptation and Mammalian Populations 261 



I. Introduction 261 



II. Endocrine Responses to Social Pressures and to Population Density- - 263 



A. Experiments in the Laboratory with Populations of Fixed Sizfc_-_ 263 



B. Freely Growing Populations 281 



C. Natural Populations 300 



III. Conclusion 325 



References 328 



General Introduction 



Endocrine adaptive responses have become of particular interest to the 

 mammalogist in recent years because of the likelihood that they play an 

 important role in the regulation of the growth of mammalian populations. 

 Sufficient evidence has accumulated from the field and laboratory to war- 

 rant stating with fair certainty that these adaptive mechanisms are opera- 

 tive in and related to changes in the size of mammalian populations. 

 However, there is still considerable uncertainty about their precise role and 

 relative importance in the regulation of population growth, especially with 

 regard to generalizing to a large number of species from the few species for 

 which data are presently available. There also exists a great deal of un- 



* Note added in proof. For additional references pertaining to recent work on endocrines 

 and population, the reader is referred to Christian (1961, 1963a & b). 



189 



