54 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



Hill (1960) says that captive Night Monkeys may moisten the 

 palms of their hands and the soles of their feet with urine, and 

 he compares this habit to the similar pattern of nocturnal Lorisoids 

 which has been interpreted as a method of marking territory. I never 

 saw anything like this in any of the Night Monkeys that I studied. 

 It may be confined to other populations of the species and/or a result 

 of special conditions in captivity. 



I might add, in this connection, that I have never seen such behavior 

 performed by Tufted Capuchins (Cebus apella) kept in captivity on 

 Barro Colorado or in the Zoo at Lima, Peru, although Nolte (1958) 

 reports it as common among some individuals of the same species 

 kept in captivity in Rio de Janeiro. This sort of behavior may be 

 extremely variable among Platyrrhini. 



COPULATIONS, ALLOGROOMING, AND ASSOCIATED PATTERNS 



Like many other New World primates. Night Monkeys seem to 

 perform overt copulatory reactions rather infrequently under natural 

 conditions. I never saw copulations by the wild individuals on Barro 

 Colorado Island. Copulations are also at least relatively rare among 

 captive individuals. The only captives observed to perform copulatory 

 reactions or closely related patterns were the ones on Barro Colorado 

 Island. Even here, the copulatory reactions of mated individuals kept 

 together continuously were not only rather infrequent but also rapid, 

 brief, and inconspicuous. The only really elaborate and conspicuous 

 sequences of copulatory patterns were performed by males and fe- 

 males coming together for the first time or rejoining one another after 

 being separated and kept in isolation for several weeks or months. 



The most simple forms of apparently successful copulations are 

 simple indeed. In such cases, the male and female tend to approach 

 one another silently. The male usually sniffs at the female's genital 

 or perineal region, either immediately or after sniffing at her face. 

 The female may sniff at his perineal region while he sniffs at hers. 

 He then mounts her from the rear, clasps her around the upper part 

 of her body with his arms, and maneuvers his body into a position 

 from which he can insert his penis into her vagina under her tail (she 

 may lift her tail, or shift it sideways, as he does so, but this move- 

 ment is always very slight). After insertion, the male usually makes 

 three or four pelvic thrusts. Ejaculation apparently occurs only 

 during the last thrust, which sometimes is sustained relatively long. 

 The whole lower part of the male's body may quiver visibly during 

 this last thrust. The male then dismounts. Sometimes his dismounting 

 seems to be accelerated by the female turning her head to look at him. 



