1314 



HORMONAL REGULATION OF BEHAVIOR 



pick up their kittens by the nape of the 

 neck (Leyhausen, 1956) . Various species of 

 rodents characteristically pick up the young 

 with the mouth, seizing them in the middle 

 of the back, by the skin of the belly, or on 

 the flank (Curio, 1955; Eibl-Eibesfeldt, 

 1958) . At least in the domestic rat, consid- 

 erable individual differences can be seen, 

 these animals having been seen to pick up 

 young by about 20 different parts of their 

 bodies (Wiesner and Sheard, 1933; Causey 

 and Waters, 1936) . Retrieving of the young 

 may be done very vigorously and persist- 

 ently. One European yellow-necked mouse 

 has been seen to retrieve, in quick succes- 

 sion, 148 young which had been placed in 

 different parts of the living space by the 

 experimenters (Zippelius and Schleidt, 

 1956). 



Some mammals use methods of retrieving 

 the young other than carrying them in the 

 mouth. Some opossums carry their young on 

 the back (Wunder, 1937). Blair (1941) ob- 

 served that young northern pigmy mice be- 

 come attached to the nipples of the mother 

 and are dragged about wherever she goes. 

 Similar methods are seen in some bats, in 

 which the young either cling to the under- 

 side of the mother's body or attach them- 

 selves to the nipple, and are carried by the 

 mothers on their hunting trips (Wunder, 

 1937; Hamilton, 1939). Beach (1939b) re- 

 ported that young Central American opos- 

 sums remain continuously attached to the 

 mother's nipples. When one of the young 

 becomes detached, the mother noses it back 

 under her belly, upon which the young ani- 

 mal rolls over on his back, grasps the moth- 

 er's ventral hair, and moves over her ven- 

 tral surface until it finds a nipple and 

 becomes attached. 



Young bicolored white-toothed shrews 

 sometimes follow the mother in a "cara- 

 van," in which the first young grasps the 

 mother's tail near its base, and the suc- 

 cessive young each similarly grabs in its 

 mouth the tail of the young in front of it 

 (Wahlstrom, 1929; Zippelius, 1957). 



In some aquatic mammals, the mother 

 may retrieve the young by swimming after 

 them and guiding them back into place 

 when they get too far away. When the 

 young bottle-nosed dolphin strays from its 

 mother's side she swims after it and pushes 



it gently, guiding its direction until it is 

 close to her side again (Tavolga and Es- 

 sapian, 1957) . Mother dolphins support the 

 young to the surface after parturition (Mc- 

 Bride and Hebb, 1948; :\lcBride and Kritz- 

 ler, 1951), and mother dolphins have been 

 seen thus supporting dead young or the re- 

 mains of dead young (Hubbs, 1953; Moore, 

 1955). 



The domestic rabbit does not seem to re- 

 trieve its young (Ross, Denenberg, From- 

 mer and Sawin, 1959), unlike rats which do 

 retrieve, although both nest in burrows. 



Retrieving by the male. In most mam- 

 mals the mother alone attends to the rear- 

 ing of the young, the father paying little 

 or no attention to them (Bourliere, 1954; 

 Hediger, 1955). In some species, however, 

 retrieving of young by the male has been 

 noted. Horner ( 1947 1 reported that male 

 deer mice in captivity often retrieve the 

 young, and Frank (1952) observed the same 

 thing in the common vole of Europe, as did 

 Leblond (1940) in the domestic mouse. On 

 the other hand, the male laboratory rat, at 

 least under the conditions in which such 

 animals are normally kept in the labora- 

 tory, does not appear to retrieve the young 

 (Seitz, 1958). ^lale Galapagos sea lions 

 take part in the care of the young, shep- 

 herding them back to shore when they swim 

 far off (Eibl-Eibesfeldt, 1955c), in contrast 

 to most seals, in which the male pays no 

 attention to the young (Bartholomew, 1952, 

 1953). 



£. Physiologic Regulation of Retrieving Be- 

 havior 



Correlation of retrieving behavior and 

 PHYSIOLOGIC CONDITION. There is consider- 

 able evidence that the tendency to retrieve 

 young is linked to, or somehow dependent 

 on, the physiologic conditions associated 

 with the end of pregnancy and the period 

 of lactation. Rabaud (1921a, b) found that 

 pregnant domestic mice began to retrieve 

 young mice offered by the experimenter at 

 about the middle of pregnancy (9 or 10 

 days) . He noted further that retrieving be- 

 comes more intense just after parturition, 

 and that, when a pregnant female and a 

 recently postparturitive female were both 

 in a cage, the pregnant one always gave 

 way when both animals attempted to re- 



