PARENTAL BEHAVIOR 



1313 



bison and antelo})e cows swallow such large 

 mouthfuls that I was afraid they would 

 choke." The domestic rabbit is also a voraci- 

 ous placentophage (Sawin and Crary, 1953 ) . 



It is remarkable that practically no at- 

 tention has been paid to the prol)lem of how 

 a herbivorous animal is induced to become 

 carnivorous at the time of parturition. A 

 beginning is found in unpublished observa- 

 tions by Dr. Thales Martins, made at the 

 American Museum of Natural History 

 (quoted by Riess, 1950), who offered vari- 

 ous diets to groups of guinea pigs, and found 

 that pregnant females showed a significant 

 preference for meat compared with other 

 groups of these animals. Wiesner and Sheard 

 (1933) offered fetuses obtained by cesarian 

 section, with their membranes and with the 

 l^lacenta attached, to some female rats 

 which had given birth about 12 hours previ- 

 ously. The majority of these animals did 

 not respond to the fetus or placenta, al- 

 though they had, on the day before, de- 

 livered and cleaned their own young. They 

 further report that nulliparous females 

 never cleaned or ate fetuses in membranes 

 offered to them, although they accepted 

 pieces of raw meat. 



Allan and Wiles (1932) hypophysecto- 

 mized 12 pregnant cats. Eleven of these ani- 

 mals ignored the kittens at birth, doing no 

 licking, tearing of the membranes, or eating 

 of the placenta. The 12th animal abandoned 

 its kittens when they were 2 days old. Simi- 

 lar results were obtained by Smith (1954) 

 who hypophysectomized 10 pregnant rhesus 

 monkeys, and found that pregnancy and 

 ])arturition were carried through normally 

 except for unusually difficult labor (sec 

 Cross, 1959). Nine of the animals failed to 

 eat the afterbirth, although a few licked it. 

 These data certainly suggest that licking of 

 the fetus and eating of the afterbirth depend 

 on the hormonal condition of the parturi- 

 ent mother. It is to be noted that nutri- 

 tional requirements of pregnant rats differ 

 in some respects from those of nonpreg- 

 nant animals, for example, in increased need 

 for salt (Richter and Barelare, 1938), and 

 future research may show some relationship 

 between these changes in nutritional needs 

 and the tendency to lick and eat the pla- 

 centa. It should he noted that most animals 

 seem to be able to select varying diets in 



accordance with varying nutritional needs 

 (Young, 1949, 1959). When the sympathetic 

 ganglia of i^regnant cats were removed, the 

 animals did not lick or clean the kittens 

 after parturition (Simeone and Ross, 1938). 

 We might speculate on whether this is due 

 to an effect of maternal sympathectomy on 

 the characteristics of the kitten, on those 

 characteristics of the mother's body which 

 lead to self-licking, or on characteristics of 

 her central nervous system. 



Mothers may occasionally eat their neo- 

 nate young. This happens not infrequently 

 in the domestic rat (Wiesner and Sheard, 

 1933) and in the domestic mouse (Brown, 

 1953), and is also seen in the domestic rab- 

 bit (Sawin and Crary, 1953). It is not clear 

 what factors contribute to this form of 

 cannibalism, although usually the eating of 

 the infant follows the eating of the placenta 

 and umbilical cord (Wiesner and Sheard, 

 1933). Indeed, in an animal which is, at the 

 moment, so voraciously carnivorous, the 

 question of why the mothers do not usually 

 eat their young may be just as reasonable 

 a question as that of why the mothers some- 

 times do eat them. Eibl-Eibesfeldt (1958), 

 on the basis of his (nonexperimental) ob- 

 servations of parturitions in the domestic 

 rat, believes that the eating of the young is 

 inhil)ited by a vocalization emitted by the 

 young, which is in part stimulated by the 

 mother's eating of the umbilicus. 



It is clear that the behavior of the mother 

 toward the newly born young and toward 

 the placenta, particularly in herbivorous 

 animals, presents a number of problems the 

 investigation of which is now at its earliest 

 stage.- 



C. RETRIEVING OF THE YOUNG 



1. Retrieving Behavior 



The retrieving to the nest of young which 

 have strayed or become scattered is charac- 

 teristic of many species of mammals (Cau- 

 sey and Waters, 1936; Wunder, 1937). Dif- 

 ferent species normally have different ways 

 of managing to retrieve the young. Every- 

 one is familiar with the way domestic cats 



" Much additional information on parturition 

 may hv found in the monograph by SUjper (1960), 

 which appeared too late to be considered in the 

 preparation of this chapter. 



