NO, 5 BEHAVIOR OF THE NIGHT MONKEY — MOYNIHAN 4I 



form — see accompanying figures — and gruntlike patterns are wide- 

 spread among many species of New World monkeys.) 



It should be mentioned, in this connection, that the Gulps of Night 

 Monkeys are uttered in almost exactly the same social circumstances 

 as the contact notes of some species of Panamanian birds, and that 

 the latter seem to have had a similar evolutionary history, also being 

 derived from purely hostile patterns (Moynihan, 1963a). 



The development of Gulps as contact notes may be another adapta- 

 tion to nocturnal habits. Night Monkeys probably cannot keep in touch 

 with their companions by sight as easily as can other platyrrhines. 



(While recording the sounds of captive Night Monkeys on Barro 

 Colorado Island, a few short and single "twanging" noises were heard, 

 through the earphones of the recording machine. Unfortunately, these 

 noises were always heard at times when the animals were not under 

 observation. They probably were not mechanical in origin [at least, I 

 could not find any object in the animals' cage which looked as if it 

 could be used to produce such noises] ; but nothing similar was heard 

 in other circumstances. To my ears, the noises sounded as if they 

 might be Gulps uttered in very close proximity to the microphone. 

 This theory does not, however, seem to be supported by sound 

 spectrograms [see figure 12]. The significance of these noises remains 

 problematical.) 



One captive Night Monkey at Iquitos uttered series of gulping 

 notes which had a distinctive hooting quality (rather as if "ooo" 

 sounds were superimposed upon the ordinary Gulps of Barro 

 Colorado animals). These notes were uttered while the animal was 

 moving about its cage in a perfectly normal manner. They may have 

 been a characteristic pattern of the local population of Night Monkeys, 

 or an individual peculiarity, or (possibly) intermediates between 

 typical Gulps and typical Hoots. 



Both the wild and captive animals on Barro Colorado Island were 

 heard to utter Sneeze-grunts. 



A single Sneeze-grunt sounded like a single sneeze superimposed 

 upon a single, loud, typical Gruff Grunt. The sound was always sharp 

 and abrupt. Most Sneeze-grunts were also at least slightly nasal in 

 tone (each note might be transcribed by something like "Aaanh"). 

 Figure 9 includes a sketch of a sound spectrogram of a more or less 

 typical Sneeze-grunt. 



Sneeze-grunts were usually uttered singly. Sometimes two were 

 uttered together in quick succession ; but they never occurred in longer 

 series Hke Gulps and Gruff Grunts. 



They were uttered with the mouth closed or nearly closed, and 



