NO. 5 BEHAVIOR OF THE NIGHT MONKEY MOYNIHAN 1 7 



One comment may be inserted here. Experience has demonstrated 

 that ritualized patterns performed by captive individuals are always 

 found to be part of the "natural" repertory of the species, performed 

 by wild individuals under natural conditions, when it is possible to 

 study the behavior of wild individuals in detail. This is certainly true 

 for all the other New World monkeys that I have been able to observe 

 at length both in captivity and in the wild. Captive animals may per- 

 form displays in situations that are different from those in which wild 

 animals perform the same displays (see also below), but they do not 

 perform displays that are not also performed by wild animals in some 

 situations. Thus it is safe to assume that wild Night Monkeys also 

 perform Swaying, although I did not actually observe it during my 

 relatively brief observations in the wild. 



The Swaying of the captive animals was frequently followed by 

 overt escape. This, and the fact that it was apparently always pro- 

 voked by the sight of a predator or potential predator, would indi- 

 cate that it was produced by activation of the escape tendency. It 

 seems likely, however, that some other tendency was also involved, 

 as all or most other ritualized patterns of Night Monkeys and other 

 species are produced when at least two tendencies are activated simul- 

 taneously. If so, the other tendency was probably attack, as some 

 Swaying was accompanied by Gruff Grunts, and these notes certainly 

 include an attack component (see below). If attack was activated 

 during silent Swaying, it was obviously much weaker than escape, 

 but it may have been relatively slightly stronger than in the previously 

 described unritualized overt escape and alarm patterns. There was 

 no indication of any significantly close or regular association between 

 Swaying and any other type of social ("friendly" or sexual) behavior. 



Swaying may discourage predators by letting them know that they 

 have been seen. An alerted Night Monkey should have no difficulty 

 in escaping from any natural predator. Night Monkeys are lighter, 

 more rapid, and/or capable of leaping greater distances than any sym- 

 patric species of carnivore. Most of the individual carnivores in any 

 given area must be well aware of this fact. Thus a carnivore that sees 

 a Swaying (and obviously alerted) Night Monkey probably will not 

 bother to chase it. This, in turn, means that the monkey will not have 

 to waste time by escaping. 



It seems likely that ritualized Swaying has been derived, in the 

 course of evolution, from unritualized "peering." Some of the side- 

 ways components of Swaying may also have been derived from inten- 

 tion movements of turning away (from an alarming stimulus). 



