82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



jump up and down and break off branches in rage (this may be 

 correlated with the small size of the species) ; and the apparent 

 absence of "displacement" scratching or grooming. 



Most of the vocal patterns of infants are high pitched and com- 

 pletely intergrading. Infants may be able to afford such behavior be- 

 cause they are always in close contact with their parents. The effects 

 of their vocalizations may be supplemented and reinforced by tactile 

 and visual stimuli. 



Some of the display patterns of Night Monkeys are particularly 

 reminiscent of howler monkeys (Alouatta), titi monkeys (Cal- 

 licehus), and/or tamarins (Saguinus). 



ACKNOWLEDGMENTS 



I am greatly indebted to many people for assistance in studying the 

 vocal patterns. In particular, Dr. W. John Smith helped with the 

 recordings, made the spectrograms on the "Sonagraph," and contrib- 

 uted many useful suggestions and criticisms. D. K. North and Miss 

 J. Arnold provided technical assistance. The other spectrograms were 

 made by Martin S. Brewer ; I must thank Mrs. Helen Hayes for help- 

 ing to arrange this. Dr. Brian Patterson and Dr. A. S. House gave 

 helpful advice and explained some puzzling features of the spectro- 

 grams. Dr. J. D. Pye very kindly provided assistance and equipment 

 in an effort to detect ultrasonic notes or calls. 



I am also grateful to Dr. Theodore H. Reed and J. Lear Grimmer 

 for facilitating work in the National Zoological Park, to Charles 

 Hawkshead for permitting me to observe his animals in Iquitos, to 

 Richard W. Thorington, Jr., for useful information on the skin 

 glands of Night Monkeys, and to Dr. John H. Kaufmann and 

 David Fairchild, 2d, for assistance in the field and in the laboratory 

 on Barro Colorado Island. 



BIBLIOGRAPHY 



Allen, J. A. 



1916. Mammals collected on the Roosevelt Brazilian Expedition, with field 

 notes by Leo E. Miller. Bull. Amer. Mus. Nat. Hist., vol. 35, 

 pp. 559-610. 

 Altmann, Stuaet a. 



1959. Field observations on a howling monkey society. Journ. Mamm., 

 vol. 40, pp. 317-330. 



