78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I46 



also try to bite when handled, and perform other overt unritualized 

 attack and escape patterns like those of adults as soon as they have 

 developed adequate coordination of the limbs. 



Changes in behavior between the infantile stage and maturity were 

 not studied in detail, as it was not considered advisable to do much 

 experimental work with the young animals being raised in captivity. 

 (In any case, there are indications that at least some patterns develop 

 at different rates in captivity and in the wild — see above.) Intermittent 

 observations of the captive animals did, however, reveal the following. 



The young animals gradually lost their desire to be carried by a 

 parent. This process seemed to be completed by the time that they 

 were approximately half grown (at the age of 6 or 7 months). By 

 the time that they were a year old, they usually objected violently to 

 being touched by the human beings whom they had regarded as parents 

 earlier. 



It was my impression that all or most of the signal patterns of 

 young animals were essentially the same as those of adults by the time 

 that they were half grown, with the exception of the strictly sexual 

 patterns and the Squeaks. The young animals continued to direct 

 many Squeaks toward human beings with whom they were familiar 

 until they were approximately 1 to 1| years old. All or most of the 

 later Squeaks seemed to be essentially friendly "greeting" patterns. 

 Many of them were closely associated with social sniffing. 



The obviously subadult individuals observed in the forest on Barro 

 Colorado Island also tended to utter more Squeaks than adults. 



Two immature Night Monkeys at Iquitos performed a variety of 

 signal patterns in addition to the Hoots already mentioned. They 

 were observed to perform Swaying and to utter typical Gruff Grunts 

 and Screams like those of adults on Barro Colorado Island. They 

 also uttered many Squeaks like those of young animals of similar age 

 (or stage of development) on Barro Colorado. 



PREVIOUS DESCRIPTIONS OF NIGHT MONKEY 

 BEHAVIOR PATTERNS 



A number of signal patterns of Night Monkeys have been described, 

 more or less briefly, in previous publications. Some of these descrip- 

 tions have been cited above. It may be useful, however, to mention 

 some others, try to identify and classify the described patterns accord- 

 ing to the terminology used in this paper, and discuss some apparent 

 discrepancies and problems. 



