GONADAL HORMONES AND SOCIAL BEHAVIOR 



1241 



Scott, 1945), or what Schneirla (1946j in- 

 cludes under trophallactic relationships. 



Social organizations can be classified into 

 two general categories: social hierarchies 

 and territories. Some species show either 

 one or the other seasonally or throughout 

 the year, whereas others may have elements 

 of both concurrently. Still others have ter- 

 ritories during the reproductive phase and 

 hierarchy during the rest of the year. Once 

 established, or even during the incipient 

 stages, a pattern of social organization is 

 typical for a given species. The variation 

 is considerable from species to species, al- 

 though comparable types of organization 

 are found throughout the vertebrates. 



Allee (1952) recognized two major kinds 

 of hierarchies: one based on unidirectional 

 (despotic) domination and the other based 

 on relative despotism in which pecking be- 

 tween any two individuals is bidirectional. 

 The former is often referred to as a "peck- 

 right" system, in which the individuals are 

 ranked in an order according to the number 

 of individuals each can dominate without 

 any attack or threat in return. Such a domi- 

 nance order is usually quite stable, and 

 species so organized are suitable for ex- 

 perimentation insofar as controlled situa- 

 tions can be maintained. A hierarchy based 

 on bidirectional pecking is more fluid be- 

 cause there is an exchange of aggressive 

 acts, and the individual delivering the most 

 "pecks" is considered the dominant mem- 

 ber of the pair. In species so organized there 

 is an overlap with territoriality, inasmuch 

 as each individual becomes more dominant 

 as it approaches the center of its territory. 



Credit for the development of the con- 

 cept of territoriality is usually given to 

 Howard (1920), although Lack (1953) and 

 Carpenter (1958) cite even older reports in 

 which some aspects of this behavior were 

 recognized. Evidences of territoriality are 

 often reported in studies on reproductive be- 

 havior and have been found in ^-arious 

 classes of vertebrates. 



Territorial organization has many forms, 

 depending on how it functions for a par- 

 ticular species. It is often defined as "a 

 defended area." However, there is no evi- 

 dence that it is the area per se that is de- 

 fended. According to Emlen (1957), "the 

 term territory is generally applied to an area 



or space in which a particular animal is 

 aggressive and largely if not supremely 

 dominant with respect to certain categories 

 of intruders." The biologic significance of 

 territory for birds has been discussed by 

 Hinde (1956a), and for all vertebrates by 

 Carpenter (1958). The latter concluded 

 that territoriality apparently, when once 

 established, reduces stress, pugnacity, and 

 nonadaptive energy expenditure. 



Aggressive behavior has the tendency to 

 disperse the individuals, as manifested in 

 territorialism. Such behavior is mediated by 

 hormones. Some behavior patterns operate 

 in the opposite direction and result in ag- 

 gregations by members of the species (Allee, 

 1931). No gonadal hormones have been 

 discovered which influence gregariousness 

 (other than sexual and parental bonds). 

 Emlen (1952) discussed the social forces 

 which cause the centripetal and centrifugal 

 actions in flocks of birds, and concluded that 

 flocking responses have their physiologic 

 basis in stereotyped neural patterns and are 

 influenced by hormonal factors only so far 

 as these incite disruptive responses as- 

 sociated with sexual or parental activity. 



Tendencies to aggregate or to disperse 

 may be seasonal or diurnal (Emlen, 1952), 

 and physical factors such as temperature 

 and light may exert an action (Allee, Em- 

 erson, Park, Park and Schmidt, 1949, p. 

 393). Species of vertebrates vary in the 

 relative distance at which one individual 

 will tolerate the presence of another. Hcdi- 

 ger (1950, p. Ill) calls this "individual 

 distance" and distinguishes betw^een "dis- 

 tance animals" and "contact animals." The 

 relative proximity at which chaffinches tol- 

 erate each other varies with dominance rank 

 and with sex (Marler, 1956). Dominant fe- 

 males allowed subordinate females to come 

 closer than other females, and males per- 

 mitted females to come closer than males. 

 Submissive behavior promotes toleration. 

 The forces of mutual attraction may de- 

 velop early in life (Collias, 1952, 1956) by 

 mechanisms that suggest imprinting (Lo- 

 rcnz, 1935). 



In many instances changes in agonistic 

 behavior appear to precede sexual behavior 

 and thereby to prepare the proper social en- 

 vironment for sexual and parental behavior. 

 IVIoynihan (1958) described the behavior of 



