48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



described by Hill, Appleyard, and Auber (1959) and Hanson and 

 Montagna (1962). Apocrine glands are largest in the face and 

 genital areas. Lateral to the alae of the nose they are intermingled 

 with large sebaceous glands. There are also larger and more spe- 

 cialized glandular organs in the sternal region and at the base of the 

 tail. It is possible that individuals which appear to be sniffing in the 

 armpits of their "partners" are really trying to get at their sternal 

 organs. 



When complete strangers are introduced to one another, they may 

 repeat social sniffing whenever they come close to one another during 

 the first few hours (or nights) after the introduction. This behavior 

 may disappear, gradually, as the animals become familiar with one 

 another. Only in the case of males and females that become mated 

 to one another does social sniffing remain frequent in certain situa- 

 tions. Mates often perform social sniffing immediately before copula- 

 tion and related patterns (see below). 



Social sniffing was performed by all the captive animals observed, 

 at Washington and Iquitos as well as on Barro Colorado Island, It 

 seemed to be performed with approximately equal frequency by all 

 individuals in similar circumstances in captivity. 



Very tame, hand-reared individuals in captivity on Barro Colorado 

 Island sniffed at human beings occasionally, especially if they were 

 familiar with the person involved but had not been visited by him or 

 her for some time. 



Although social sniffing may be followed by high-intensity hostile 

 behavior as well as (or instead of) copulatory reactions and may be 

 accompanied by a variety of vocalizations, such as Trills and Squeaks, 

 it is probably purely investigatory in itself. The first part (at least) 

 of social sniffing seems to be essentially the same as the sniffing of 

 food described above. 



SEXUAL BEHAVIOR AND ASSOCIATED OR 

 RELATED PATTERNS 



The term "sexual behavior" will be used in a broad and general 

 sense throughout the following pages to include all behavior patterns 

 characteristically directed by adult individuals of one sex toward 

 adults of the other sex, or performed by adults of one sex in the 

 presence of the other. 



The causal factors responsible for the performance of sexual ac- 

 tivities by Night Monkeys are particularly difficult to identify, even 

 tentatively, for several reasons. 



In many species of higher vertebrates, all or most sexual activities 



