1256 



HORMONAL REGULATION OF BEHAVIOR 



of the lower mammals that have been stud- 

 ied, the female is submissive when follicular 

 development is at its height, and resistant to 

 the male or even strongly aggressive at 

 other times. This was long ago noted in the 

 female guinea pig (Young, Dempsey and 

 Myers, 1935) and has more recently been 

 recorded for other species. The female opos- 

 sum has been observed after a heat period 

 to attack and kill a male double her weight 

 (Hartman, 1945). Pearson (1944) states 

 that the nonreceptive female short-tailed 

 shrew faces the male whenever he is near 

 and repulses his advances with lunges, loud 

 squeaks, and sometimes a long, shrill chat- 

 ter. Evans' (1937) observation that ovariec- 

 tomy of the lizard, Anolis carolinensis, in- 

 creased the territorial response, may not be 

 unrelated. The change in behavior at estrus, 

 such as that described for the guinea pig, 

 opossum, and shrew, was made the subject of 

 an investigation by Kislack and Beach 

 (1955). Intact, estrous and diestrous fe- 

 males, and estrogen-treated spayed animals 

 were tested in pairs with males. Spayed 

 hamsters were continually aggressive, al- 

 though somewhat less so than intact di- 

 estrous females. The administration of 

 estrogen alone was followed by a slight in- 

 crease in aggressiveness, but progesterone 

 injected after estrogen eliminated fighting 

 and reduced other forms of aggression. 

 Progesterone alone had no influence on the 

 behavior of spayed hamsters. It was con- 

 cluded that there is a negative relationship 

 between sexual receptivity and aggressive- 

 ness, w^iich depends in large measure on 

 ovarian secretions. In the words of the au- 

 thors, the ovarian hormones that render the 

 female receptive also inhibit her tendency 

 to attack the male. 



In other experiments the results of treat- 

 ment with estrogens were ambivalent or 

 negative. Allee and Collias (1940) injected 

 estradiol into intact hens and discovered 

 only a slight tendency toward reduced ag- 

 gressiveness and lowered status in the peck- 

 order, even w^hen large amounts were given. 

 Both male and female chicks of the domestic 

 fowl injected with an estrogen formed a 

 hierarchy which was determined largely by 

 avoidance reactions (Guhl, 1958). Individ- 

 uals of both sexes gave the submissive sex- 



ual crouch when a hand was held over them. 

 Pecking was rare and the social order was 

 called an avoidance-order rather than a 

 peck-order. Emlen and Lorenz (1942), on 

 the other hand, did not observe a behavioral 

 response in valley quail given estrogen. 

 Shoemaker (1939) and Noble and Wurm 

 (1940) also obtained negative results with 

 canaries and night herons, respectively. 



Young rhesus monkeys were tested with 

 an androgen and an estrogen (Mirsky, 

 1955). Unisexual social groups of 5 were 

 organized on a hierarchial system. Those 

 in ranks 5 and 2 received implanted pellets 

 of the androgen or the estrogen in two dif- 

 ferent periods separated by an interval 

 without treatment. Two pairs of males and 

 two pairs of females of known dominance 

 relations were tested. The subordinate mem- 

 ber of each pair was given either androgen 

 or estrogen. In no case was hormone admin- 

 istration accompanied by a significant de- 

 crease in either dominance or subordinate 

 l)ehavior scores. 



Except for the report that a prepubertally 

 castrated male showed enhanced dominance 

 status under androgen therapy, and sub- 

 ordinate status as a result of estradiol ad- 

 ministration (Clark and Birch, 1945), in- 

 vestigations on the chimpanzee have yielded 

 results that are not clear. According to 

 Yerkes (1939), the importance of the sexual 

 condition was established. The dominant 

 female of a pair, w^hen in estrus, ordinarily 

 grants privilege to her subordinate com- 

 panion, whereas the subordinate female, 

 when in estrus, may achieve privilege and 

 act as if temporarily in control. The state- 

 ment is not made that the subordinate mem- 

 ber of a pair becomes dominant when she is 

 in estrus. Crawford (1940) provided addi- 

 tional evidence that a response priority in 

 a food competition situation is related to the 

 sexual status of the females. In 9 of 13 pairs 

 in which changes in response priority oc- 

 curred, the subordinate member obtained 

 food more often when in the follicular phase 

 of the cycle. Again, the behavior was de- 

 scribed as a yielding of priority by the dom- 

 inant subject with only the weak suggestion 

 of an increase in aggressiveness on the part 

 of the subordinate animal. However, Birch 

 and Clark (1946, 1950) and Clark and 



