1262 



HORMONAL REGULATION OF BEHAVIOR 



competition and fighting increase as the 

 population increases and this results in a 

 number of responses including the hyper- 

 trophy of the adrenal cortex. A number of 

 ensuing responses reduces the reproductive 

 rate and increases mortality. Thus reproduc- 

 tion is reduced or, if the behavior patterns 

 and physiologic responses are not precisely 

 adjusted, a population decline may occur. 

 In this manner, behavior acts as a homeo- 

 static mechanism for populations. 



Conceivably, this important generaliza- 

 tion is premature, at least in this form. The 

 extensive data on the Iowa muskrat, On- 

 datra zibethicus (Errington, 1957), do not 

 indicate that social stress is a major factor 

 in the population cycle of this species. There 

 may be other exceptions. In addition, the 

 application of newer tests of adrenal func- 

 tion would be desirable. 



IX. Concluding Remarks 



Much work has been done in an effort to 

 ascertain whether a relationship exists be- 

 tween gonadal hormones and the social be- 

 havior which is displayed so conspicuously 

 at the time of reproduction. There will be 

 disappointment that more exact information 

 has not been obtained. This can be explained 

 in part by the circumstance that endocrino- 

 logic, neurologic, and psychologic processes 

 of the most complex types are involved. 

 Such being the case, any analysis of the 

 many problems requires the utilization of 

 endocrinologic, neuroanatomic, neurophysi- 

 ologic, and psychologic techniques. Unfor- 

 tunately, however, application of the rigor- 

 ous tests which are a part of these techniques 

 has not been possible. The end points thus 

 far available to the investigator of social 

 behavior are not as sharp as those on which 

 the endocrinologist would insist; neural 

 centers which might be inactivated or stim- 

 ulated electrically or chemically are not 

 known to exist, and the psychologist is 

 handicapped by the variables inherent in 

 any study of a behavior involving interac- 

 tion with other animals. On the other hand, 

 it may be expected that as more work is 

 done, the handicaps imposed by these re- 

 strictions will be overcome and a more 

 gratifying progress may be anticipated. 



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