PARENTAL BEHAVIOR 



1353 



not begin incubating until the full clutch 

 had been laid. The kittiwake, a species of 

 gull, differs from other gulls with respect 

 to many behavior patterns, most of them 

 adaptations to the kittiwake's peculiar (for 

 a gull) habit of nesting on cliffs (Cullen, 

 1957). For example, in most gulls, the 

 l)arent regurgitates food for the young, 

 which picks it up from the ground; the 

 young kittiwake takes the food directly 

 from the bill of its parents. 



Differences in hormonal mechanisms in 

 different animals. Beach (1958a) points out 

 that identical hormone treatment may, in 

 many cases, cause quite different forms 

 of behavior in different kinds of animals, 

 and that the evolutionary changes in be- 

 havior between different species have there- 

 fore affected, not the nature of the endo- 

 crine mechanisms inducing the behavior, 

 but rather the nature of the neural and 

 o^her structures which respond to the hor- 

 mones. For example, injection of testos- 

 terone propionate induces male sex be- 

 havior in valley quail (Emlen and Lorenz, 

 1942) and in ring doves (Bennett, 1940); 

 but the form of the behavior which is in- 

 duced is quite different in the two species. 



However, in spite of the fact that the 

 nature of the endocrine secretions does not 

 appear to change very much during evolu- 

 tion (at least in warm-blood animals) , there 

 are many cases in which the patterning of 

 these secretions and the nature of the so- 

 matic responses are very different in dif- 

 ferent animals. We may thus find cases in 

 which the nature of the endocrine mecha- 

 nisms underlying various behavior patterns 

 itself changes, or is different in different 

 types of animals. 



Eckstein (1949) points out that different 

 species of mammals show very different re- 

 lationships between environmental cycles 

 and the reproductive system. Thus, some 

 breed in spring, some in the autumn, and 

 some breed aperiodically. Some ovulate 

 spontaneously, some only on stimulation 

 (Asdell, 1946). In addition to species dif- 

 ferences in the way in which endocrine pat- 

 terns themselves occur, there are striking 

 differences in the ways in which the hor- 

 mones influence behavior in different spe- 

 cie*. For example, ]\Ioore (1920) trans- 



planted ovaries into castrated young rats 

 and guinea pigs. When adult, the rats 

 showed female-like maternal behavior to- 

 ward young animals, although no such be- 

 havioral changes were induced in the guinea 

 pigs. Pregnant mice build substantial nests 

 starting about the middle of pregnancy, 

 whereas the corresponding behavior in rats 

 does not occur until just before parturition 

 (Roller, 1952; Wiesner and Sheard, 1933). 

 This suggests that the hormonal basis of 

 nest-building is different in the two species. 

 Progesterone induces nest-building in mice 

 (Roller, 1956), although it does not appear 

 to have this effect in rabbits (Zarrow, Sawin, 

 Ross and Denenberg, unpublished). Indeed, 

 the fact that experimental removal of the 

 corpus luteum during pregnancy induces 

 nest-building behavior in the rabbit (Rlein, 

 1956) suggests that progesterone might have 

 quite opposite effects in the rabl)it and in 

 the mouse. 



In birds, too, there are many examples 

 of different hormonal responses to similar 

 situations, and of different effects of hor- 

 mones on patterns of behavior, in different 

 species. Rept under similar conditions of 

 light and temperature, ring doves breed all 

 year, and the related mourning dove breeds 

 only in the spring and summer (Cole, 1933) . 

 When sitting on infertile eggs, mourning 

 doves abandon the nest after about 17 days, 

 whereas domestic pigeons continue to sit 

 for about 22 days (Cole and Rirkpatrick, 

 1915). Progesterone, which induces incuba- 

 tion behavior in ring doves (Riddle and 

 Lahr, 1944; Lehrman, 1958b), has no effect 

 on incubation behavior in chickens (Riddle, 

 1937) or canaries (Robayashi, 1952; Ro- 

 bayashi and Okubo, 1954). Testosterone 

 propionate interrupts established broodiness 

 in hens, but seems to have no effect on 

 established incubation behavior in pigeons 

 (Collias, 1940, 1950). Treatment with estro- 

 gen and prolactin, which induces the forma- 

 tion of the incubation patch in finches 

 (Bailey, 1952), fails to induce it in the cow- 

 bird, which normally does not incubate eggs 

 (Selander, 1960). Since the pituitary glands 

 of cowbirds have been found to contain pro- 

 lactin (Hohn, 1959), the failure of brood- 

 patch formation in these parasitic birds is 

 apparently due to the fact that the ventral 



