SOME BEHAVIOR PATTERNS OF 



PLATYRRHINE MONKEYS 



I. THE NIGHT MONKEY 



(Aotus trivirgatus) 



By M. Moynihan 



Director, Canal Zone Biological Area 



Smithsonian Institution 



This is the first in a series of papers on some behavior patterns of 

 New World monkeys. The main emphasis of these papers will be 

 comparative. Special attention will be paid to social signal patterns 

 (including hostile and sexual signals) and other patterns that differ 

 significantly in the various species. It is hoped that analyses of these 

 patterns may throw some light on the evolution of the group as a 

 whole. 



INTRODUCTION 



The Night Monkey (also called "Owl Monkey" or "Douroucouli") 

 is a rather small monkey of distinctive appearance. 



Although individuals vary considerably in proportions, all adults 

 have relatively small heads and more or less elongated bodies. Their 

 limbs are of moderate length, the hind limbs being somewhat longer 

 than the front. Their tails are long and heavily furred, and not at all 

 prehensile. The back, most of the head, and the outer surfaces of the 

 limbs may be gray, brown, or even reddish brown, while most of 

 the underside of the body and the inner surfaces of the limbs are 

 usually clear buff or caramel colored. The upper part of the tail gen- 

 erally is the same color as the back, and the terminal half or two- 

 thirds is blackish. The face and forehead are marked with conspicuous 

 black and white stripes and patches (see the accompanying figures for 

 an indication of the color pattern of Panamanian Night Monkeys). 

 The distinctive appearance of the face is enhanced by the very large 

 eyes. In bright light, the pupils are greatly contracted and the orange 

 or hazel irides are conspicuous. In very dim light, the pupils expand 

 enormously and the eyes appear to be completely black. 



Young Night Monkeys look more like marmosets in some ways. 

 They have relatively larger heads and shorter bodies and tails than 



SMITHSONIAN MISCELLANEOUS COLLECTIONS; VOL. 146, NO. 5 



