1254 



HORMONAL REGULATION OF BEHAVIOR 



spawning cichlid fish, Aeguidens latifrens, 

 fights the male more often than does the 

 gravid female (Breder, 1934) . Female guinea 

 pigs become submissive to, or tolerant of, the 

 male during estrus (Young, Dempsey and 

 Myers, 1935). According to Pearson (1944) 

 the female short-tailed shrew, Blarina bre- 

 vicauda, fights the male when nonreceptive, 

 but during estrus is quite docile, as is the 

 golden hamster (Kislack and Beach, 1955) . 

 Female chimpanzees become dominant (in 

 the sense of attaining a response priority 

 during food-getting tests) over other fe- 

 males during the period of maximal genital 

 swelling (Crawford, 1940). 



Not to be overlooked is the probable sig- 

 nificance of the fact that such changes in 

 behavior are seen in females, in which ovar- 

 ian activity is cyclic, rather than in males 

 in which testicular activity is continuous. 



B. ANDROGENS AND AGGRES.SIVENESS 



In most subhuman vertebrates which 

 have been observed in sociobiologic studies 

 the males are more aggressive than the fe- 

 males and aggressiveness increases during 

 the sexual development of maturing animals 

 as well as during the breeding season. That 

 early castration of domestic male animals 

 reduces pugnacity has long been known 

 (Rice, 1942). Goodale (1913) noted the lack 

 of combativeness in the capon, and Scott 

 and Payne (1934) found that castration 

 eliminates fighting in the tom of the bronze 

 turkey, Meleagris gallopavo. According to 

 Uhrich (1938), male mice castrated as 

 adults continue to fight, whereas those gon- 

 adeetomized prepubertally rarely fight. 

 Evans (1936) observed that castrated males 

 of the lizard, Anolis carolinensis, continue 

 to fight, and that females rarely fight unless 

 they are ovariectomized. From this, he con- 

 cluded that ovarian hormones inhibit fight- 

 ing. However, Greenberg and Noble (1944) 

 expressed the opinion that both sexes are 

 innately aggressive and that the seasonal 

 increase in testicular hormone in the male 

 transforms mere antagonism into territori- 

 ality. Castration of the male gobiid fish, 

 Bathygobius soporator, results in the disap- 

 pearance of combative behavior, but court- 

 ship is not impaired. Nonspawning males 

 show normal combat, and hypophysectomy 



is followed by a cessation of both combat 

 and courtship (Tavolga, 1955). A continued 

 display of pugnacity was observed in cas- 

 trated starlings, Sturnus vulgaris (Davis, 

 1957a), and in castrated male pigeons (Car- 

 penter, 1958) . Geldings ranked among mares 

 in a common dominance order (Montgom- 

 ery, 1957). These observations point to 

 androgen concentration in the blood as in- 

 fluencing the level of combativeness. Ap- 

 parently, however, the extent to which cas- 

 tration affects the level of aggressiveness 

 varies among species, and according to the 

 age at which the animal is gonadectomized. 

 The experimenter's connotation of aggres- 

 sive behavior and the method of its meas- 

 urement may result in variations in the in- 

 terpretation of the effects of castration. 



The administration of androgen often 

 produces an increase in aggressiveness in 

 normal adults and in castrates, and precoc- 

 ity in immature individuals of either sex. 

 Treatment of fishes has been followed 

 mostly by observations of sexual behavior 

 (Aronson, 1957, p. 286), but Noble and 

 Borne (1940) reported advancement in rank 

 by spayed and intact female swordtails, 

 Xiphophorus helleri, after implanting pel- 

 lets of testosterone. Juvenile and young 

 adult urodeles, Tritunis viridescens, treated 

 with whole pituitary and luteinizing hor- 

 mone (LH) fraction pre-empted first place 

 in their hierarchies (Evans, 1956). Male 

 Anolis treated with testosterone propionate 

 fought more than the controls (Noble and 

 Greenberg, 1941). Subordinate males of 

 Sceloponis grammicus received an androgen 

 (Perandrenj and rose in their respective 

 hierarchies (Evans, 1946). Among birds, 

 androgen treatment caused an increase in 

 aggressiveness in the ringdove, Streptopelia 

 risoria (Bennett, 1940), the herring gull, 

 Larus argentatus (Boss, 1943) , and in pou- 

 lards (Davis and Domm, 1943). Female 

 rats injected with androgen became irritable 

 and pugnacious (Ball, 1940; Huffman, 1941; 

 Beach, 1942). Tollman and King (1956) in- 

 jected an androgen into young gonadecto- 

 mized male and female C57BL/10 mice and 

 found that the males responded more ag- 

 gressively toward each other than did the 

 females. They concluded that either the 

 nervous systems of both sexes responded 



