NO. 5 BEHAVIOR OF THE NIGHT MONKEY — MOYNIHAN 6/ 



the second component. The rate of rise or fall may vary within the 

 same component. When a Squeak is composed of three more or less 

 distinct components, the first usually rises, the second usually rises 

 or remains approximately level, and the third usually falls. More 

 rarely, the pitch may rise or fall more or less steadily throughout a 

 whole Squeak, or may first fall and then rise. 



0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 



Fig. 15. — Four typical "pure" Squeaks, uttered by an iminature. 

 Based upon a spectrogram by a "Sona-graph." 



Some Squeaks are much louder than usual without being prolonged. 

 Patterns of this type tend to extend over a particularly wide range 

 of pitch (see figure 16). 



In some Squeaks with both rising and falling pitch the rising part 

 is loudest ; in others the falling part is loudest. 



The Squeaks of infants and young juveniles intergrade with both 

 Screams and High Trills. 



The "pure" Screams of infants and young juveniles sound similar 

 to adult Screams, but are slightly softer and perhaps slightly plain- 

 tive in tone. The most extreme Screams of the young animals that I 

 studied sounded as if they were approximately as long as the adult 

 Screams shown in figure 5, and only slightly higher in pitch on the 

 average. It is possible that infants and juveniles never utter Screams 

 of as long duration as the adult patterns shown in figure 6; but I 



