PARENTAL BEHAVIOR 



1269 



1. Taxonomic diftVitMifes in parental 



behavior and in the mechanisms 

 underlying it 1352 



2. Strain differences and genetic fac- 

 tors 1354 



E. The Role of Parental Behavior in the 



Development of the Young 1355 



1. In birds 1355 



2. In mammals 1357 



V. Scientific Names ok Animals Men- 

 tioned IN Text 1359 



A. Birds 1359 



B. Mammals 1360 



VI. References 1360 



I. Introduction 



Almost all species of birds and mammals 

 exhibit special behavior patterns the func- 

 tion of which is to warm, feed, protect, or 

 otherwise foster the development of their 

 eggs and/or young. Although these behavior 

 patterns vary widely in form, physiologic 

 organization, ontogenetic origin, and degree 

 of psychologic complexity, it is nevertheless 

 sometimes convenient to group them to- 

 gether under the rubric of "parental be- 

 havior." Such behavior is of course appro- 

 priate to, and ordinarily occurs only at, the 

 stage of the reproductive cycle when there 

 are eggs or young present or impending. Its 

 regulation is, therefore, in part, a function 

 of the reproductive cycle, and it is the pur- 

 pose of this chapter to discuss the relation- 

 ships between the (endocrine) reproductive 

 cycle and the occurrence and organization 

 of parental behavior. 



Decisions about what should be included 

 in such a discussion are not easy to make, 

 because what we call ''parental behavior" is 

 not always as clearly differentiated within 

 the animal's repertoire of behavior patterns 

 as it is in our own conceptions. For example, 

 mice of almost any age, either sex, and any 

 physiologic condition may do a certain 

 amount of nest-building, which is, to the 

 observer, only quantitatively different from 

 the more intense nest-building of the pre- 

 parturient animal. Should a detailed dis- 

 cussion of such behavior necessarily be in- 

 cluded in a chapter on "parental behavior"? 

 The nest-building of most species of birds is 

 associated with the period of maximal sex- 

 ual activity, and in some cases is incorpo- 

 rated into the courtship pattern. How do 

 we, for purposes of a book like this, draw a 

 shari) line between "sexual behavior" and 



"parental behavior"? It is obvious that such 

 decisions must sometimes be more or less 

 arbitrary. 



For the purpose of this discussion, "pa- 

 rental behavior" will include nest-building 

 and behavior toward eggs and young, ending 

 with the time at which the young are able 

 to obtain food independently of their par- 

 ents. 



It is perhaps inevitable that detailed 

 physiologic experimentation should be for 

 the most part limited to a few species of 

 animals which are cheap and easy to breed 

 in the laboratory, like rats, mice, and guinea 

 pigs; or economically important, like do- 

 mestic chickens ; or similar to human beings, 

 like monkeys and chimpanzees. This con- 

 centration of analytic work on a relatively 

 few species has the effect of partially con- 

 cealing from view the enormous diversity 

 of behavioral and physiologic patterns that 

 characterize the adaptation of animals to 

 their environment. The diversity of behav- 

 ior in different species, and of the physio- 

 logic mechanisms underlying the behavior, 

 may be just as great as is their diversity 

 of form. This is not the appropriate place 

 for an exhaustive survey of the varieties of 

 parental behavior found in nature, but it 

 may help to put the available work on hor- 

 monal regulation of such behavior into per- 

 spective if we from time to time briefly 

 indicate the types which can be found, and 

 point out that they are by no means limited 

 to those characteristic of domestic and labo- 

 ratory animals. 



II. Hormones and Parental Behavior 

 in Birds 



A. NEST-BUILDING 



1. Varieties of Nest-biiilding 



Structure and location. Each species of 

 bird has its characteristic method of pro- 

 viding a place for the deposition and incu- 

 bation of the eggs, and the variability of 

 nest construction within species is quite 

 small. Between species, however, there are 

 very wide variations. Some species build 

 only above the ground (American robin, 

 Herrick, 1911) or over water (tricolored 

 red-winged blackbird, Emlen, 1941), some 

 build only on the ground (herring gull, 



