NO. 5 BEHAVIOR OF THE NIGHT MONKEY — MOYNIHAN 49 



seem to be produced by two main types of motivation: A pairing 

 tendency, which is satisfied by the presence of a mate, and a copulatory 

 tendency, which is satisfied by the performance of a successful copula- 

 tion (or ejaculation in the case of male). Night Monkeys may have 

 the same two tendencies ; but this could not be confirmed, during the 

 present study, because of the practical difficulty of observing the 

 usual long-term sequence of sexual reactions under natural conditions. 

 In many other species of New World monkeys, it is possible to 

 distinguish between the sexual tendencies and a gregarious tendency, 

 which is satisfied by association with other adult individuals of the 

 same species irrespective of sex. This cannot be done in the case of 

 the Night Monkey, simply because adults of this species do not usually 

 associate with any other adults of the same species except their own 

 mates. It is conceivable, however, that the complex of factors produc- 

 ing the sexual behavior of Night Monkeys includes components 

 homologous with the gregarious tendencies as well as the strictly 

 sexual tendencies of related species. 



HOOTS 



Both wild and captive adult Night Monkeys on Barro Colorado 

 Island uttered Hoots. So did a subadult individual, who seemed to be 

 behaving in an essentially adult manner, at Iquitos. Among the 

 captive individuals on Barro Colorado Island, Hoots were uttered by 

 both males and females. The individual Hoots of all these animals 

 sounded similar or even identical (apart from some variation in loud- 

 ness) to my ears. 



They were low-pitched, moderately prolonged, and at least moder- 

 ately loud. Each individual Hoot sounded to me like a single note. I 

 seem to have been misled, however. A sketch of what sounded to me 

 like three Hoots is shown in figure 13. It will be seen from this that 

 each one of the apparently unitary Hoots was actually compound, 

 composed of one or two relatively long sounds, followed by two to 

 five short sounds, with only very brief intervals between them. 



In spite of this discrepancy, it will be convenient to refer to each 

 hooting pattern that sounded to me like a single note as a "Hoot" or 

 "a note." The briefer sounds making up a Hoot, in this sense, will be 

 referred to as "components of a Hoot." Using these terms, it can 

 be said that the intervals between the components of a Hoot were 

 always much shorter than the intervals between successive Hoots or 

 between a Hoot and any other type of call or note. 



(The Hoots sketched in figure 13 were uttered by an adult female. 

 Unfortunately, these were the only Hoots uttered by an adult of 



