r2()0 



HORMONAL REGULATION OF BEHAVIOR 



27) showed that the red undersides of the 

 three-spined stickleback, Gasterosteus acu- 

 leatur, elicited aggression irrespective of the 

 size or shape of the models. Apart from 

 color, a head-downward posturing was also 

 effective. The hormonal relation to color or 

 posturing was not established. In Gambusia 

 hurtadoi the intensity of yellow markings on 

 the dorsal fin, at the base of the caudal fin, 

 and on the ventral portion of the caudal 

 peduncle were correlated with rank in the 

 social hierarchy (McAlister, 1958). 



Evans (1955) discussed various types of 

 releasers found among reptiles, which in- 

 cluded postures, colors, and sounds. Many 

 of these occur only in sexually mature in- 

 dividuals. Nocturnal species tend to use 

 auditory cues whereas diurnal species do 

 much posturing, often with pigmented areas 

 drawing attention to these movements. The 

 close relationship between hostile and sexual 

 behavior patterns was shown by Greenberg 

 and Noble (1944) in Anolis carolinensis, 

 because reaction patterns may shift readily 

 from one form to the other in either direc- 

 tion. The crest in this species was stimulated 

 by testosterone propionate. 



Color in birds was one of the first of the 

 secondary sex characters to receive atten- 

 tion in its relation to agonistic behavior 

 (Huxley, 1934). The songs of birds are gen- 

 erally accepted as indicators of the repro- 

 ductive phase and often are related to terri- 

 toriality (Armstrong, 1947, p. 293). 



Lorenz (1950, p. 242) , in his discussion of 

 the subject, defined a social releaser as a 

 "device — either a property of color and/or 

 shape, or a special sequence of movements, 

 or, for that matter, of sounds, or a scent — 

 specifically differentiated to the function of 

 eliciting a response in a fellow member of 

 the species. To every releaser, as an organ 

 for sending out sign stimuli, there corre- 

 sponds a perceptual correlate, an 'organ' to 

 receive sign stimuli and to activate the an- 

 swering reaction." The latter he called a 

 releasing mechanism. The point of interest 

 is whether any of the releasers, or the so- 

 called releasing mechanisms, are influenced 

 by gonadal hormones. 



With respect to the former, when they 

 are clearly defined secondary sex characters, 

 the answer has been given in countless in- 



vestigations and reviews (see particularly 

 Lipschiitz, 1924, chapter 2; Allen, Danforth 

 and Doisy, 1939, p. 185, 251, 340, 499, 545; 

 Beach, 1948, chapter 10; and the chapters by 

 Forbes and van Tienhoven in this book). 

 Whether the functioning of releasing mecha- 

 nisms, that is, visual, auditory, olfactory, 

 and tactile receptors, and central neural tis- 

 sues, is influenced by gonadal hormones is 

 less certain. The subject is discussed at 

 length by Lehrman and Young in the parts 

 of their chapters dealing with the mechanism 

 of the hormone actions which stimulate pa- 

 rental and mating behavior. Briefly, the 

 opinion has been expressed that gonadal hor- 

 mones act on peripheral receptors (Carter, 

 Cohen and Shorr, 1947 ; Beach and Levinson, 

 1950) and olfactory sensitivity (LeMagnen, 

 1952a, b, 1953). Tavolga (1955) castrated 

 males of the gobiid fish, Bathygobius sopo- 

 rator, and noted that they act as though they 

 do not "perceive" the difference between 

 males, gravid females, and nongravid fe- 

 males. He concluded that testicular hor- 

 mones affect the threshold of visual, chemi- 

 cal, and possibly auditory sense organs. 



Particularly pertinent to the subject is 

 the discussion presented by Birch and Clark 

 (1950) following their investigation of the 

 mechanism of estrogen-induced dominance 

 in chimpanzees. As they wrote, the problem 

 centers around the differential effectiveness 

 of estrogen in producing changes in the 

 dominance status of males and females. Tes- 

 tosterone, whether given to males or females, 

 was assumed to facilitate aggressive be- 

 havior by an action on the central nervous 

 tissues. Estradiol reduced aggressive tend- 

 ency in the two sexes and the effect was as- 

 sumed to be central. But there is a second 

 effect on the female which is peripheral and 

 results in the swelling and increased irrita- 

 tion of the sex skin. The facts that domi- 

 nance-status paralleled the engorgement of 

 the sex skin, and that prevention of the 

 latter by the simultaneous administration 

 of progesterone reduced the dominance- 

 status, were the basis for concluding that 

 the peripheral effectiveness of estrogens ac- 

 counts for their effects on dominance. The 

 case is weakened, unfortunately, by the 

 authors' failure to eliminate the possibility 

 that the progesterone given to inhibit sex- 



