NOTES 

 MATERNAL INSTINCT IN A MONKEY 



ROBERT M. YERKES 



To my friend and fellow investigator, Doctor G. V. Hamilton, 

 I owe the opportunity to make the observations of the behavior 

 of monkeys which it is the purpose of this note to report. Gladly 

 I avail myself of this chance to thank him publicly for his gener- 

 osity in placing his animals and experimental equipment wholly 

 at my disposal during the present year, and for his unfailing 

 kindness and sympathy. 



On February 27 one of the monkeys of our collection gave 

 birth, in the cages at Montecito, to a male infant. The mother 

 is a Macacus cynomolgus rhesus who has been described by 

 Hamilton 1 as " Monkey 9, Gertie, M. cynomolgus rhesus. Age 

 3 years, 2 months. (She is now, May 1, 1915, 4 years and 6 

 months). Daughter of monkeys 3 and 10. First pregnancy 

 began September, 1913." The result of this pregnancy was, I 

 am informed, a still-birth. 



The second pregnancy, which shall now especially concern us, 

 resulted likewise in a still-birth. Parturition occurred Saturday 

 night, and the writer first observed the behavior of the mother 

 the following Monday morning. In the meantime the laboratory 

 attendant had obtained the data upon which I base the above 

 statements. 



At the time of parturition Gertie was in a 6 by 6 by 12 foot 

 out-door cage containing a small shelter box, with an excep- 

 tionally quiet and gentle male (not the father of the infant) 

 who is designated in Hamilton's paper as Monkey 28, Scotty. 



My notes record the following, exceptionally interesting and 

 genetically important behavior. On March 1, when I approached 

 her cage, Gertie was sitting on the floor with the infant held in 

 one hand while she fingered its eyelids and eyes with the other. 



1 Hamilton, G. V. A study of sexual tendencies in monkeys and baboons. Jour, 

 of Animal Behavior, 1914, 5, 298. 



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