NO. 5 BEHAVIOR OF THE NIGHT MONKEY — MOYNIHAN 9 



This type of terminology has been criticized on various grounds. 

 Among the most recent critics is Andrew ( 1963) . The term "tendency" 

 as used here is certainly a great oversimplification, but its convenience 

 in actual practice may outweigh its disadvantages in theory. Most 

 ethologists have been driven to use the same or a similar term, or the 

 same concept in more or less disguised form, when describing a variety 

 of different types of social behavior. 



Andrew {op. cit.) suggests that all or most signal patterns of pri- 

 mates may be caused by "stimulus contrast." This is undoubtedly true 

 — if "stimulus contrast" is defined broadly enough. But platyrrhine 

 signal patterns are certainly not produced by a single range of qualita- 

 tively similar stimulus contrasts of differing strengths. Certain stimuli 

 usually ("normally") provoke only sexual patterns, others generally 

 provoke only hostile patterns, still others usually provoke only parental 

 responses, etc. Thus the causation of platyrrhine signal patterns can 

 be described in terms of stimulus contrasts only if distinctions are 

 made between qualitatively different types of stimulus contrasts, e.g., 

 between hostile stimulus contrasts and sexual stimulus contrasts. It 

 may be doubted if such a system is any more convenient or useful 

 than the employment of terms such as tendency. It is certainly more 

 difficult to use in descriptive passages. (And, in fact, Andrew himself 

 does not use it consistently throughout his own description of primate 

 signal patterns.) 



All the vocal patterns cited in the following pages will be given 

 names, such as "Moan," "Grunt," "Gulp," etc. These names are used 

 purely for convenience. They are not meant to describe the acoustical 

 properties of the sounds in detail ; this will be done in the accompany- 

 ing drawings of sound spectrograms. They are meant only to suggest 

 that the sounds are somewhat similar (to human ears) to the common 

 human and other everyday sounds called by the same names. 



The term "sound" itself will be used in its ordinary, everyday sense 

 throughout the paper. 



All the hostile behavior patterns mentioned are those of adults, both 

 males and females, unless specifically stated otherwise. 



OVERT ATTACK BEHAVIOR 



Night Monkeys are among the most aggressive New World pri- 

 mates. Adult individuals of the same sex usually fight savagely when 

 put together in a cage. Adults of opposite sex, mates or potential 

 mates, may not engage in violent fights, but they do direct a consider- 



