NO. 5 BEHAVIOR OF THE NIGHT MONKEY — MOYNIHAN 53 



where they performed Rubbing much more frequently than elsewhere. 

 All or most of these sites were places where there was a slightly 

 projecting irregularity on the surface of a branch, or even the stump 

 of a projecting twig. 



As an intraspecific reaction, Rubbing was performed almost ex- 

 clusively during encounters between males and females, usually en- 

 counters in which either one or both individuals also performed 

 overt (and often high-intensity) hostile and copulatory patterns. Low- 

 intensity Rubbing might be performed by either one or both indi- 

 viduals during such encounters; but complete and vigorous Rubbing 

 generally was performed only by females. Most male Night Mon- 

 keys tend to be slightly dominant over females. It may be significant, 

 therefore, that the only male observed to perform high-intensity 

 Rubbing during an intraspecific encounter was obviously subordinate 

 to the female with which he was associated at the time. He would 

 seem to have been playing a feminine role. Although usually sub- 

 ordinate, the females that performed high-intensity Rubbing were not 

 very frightened. They usually did their Rubbing as they approached 

 males, to initiate either overt hostility or precopulatory behavior (or 

 both). 



Some very tame individuals performed low-intensity Rubbing 

 movements when approached by human beings. A moderately tame 

 individual (almost certainly a male), in a cage with its mate and 

 young, repeatedly performed vigorous and complete Rubbing after 

 being approached by a human being, as the latter walked away. 



These facts would suggest that Rubbing is usually produced by 

 some combination of hostile and sexual tendencies. (Some other 

 "friendly" social tendency may take the place of sex in some cir- 

 cumstances.) Possibly some territorial motivation is also involved. 

 (It is not yet clear how the motivation of Rubbing differs from that 

 of Moans or Low Trills. There is not enough evidence to permit a 

 choice among the several possibilities that come to mind.) 



Rubbing is probably related, phylogenetically, to the "territory 

 marking" patterns of many other mammals (which are very similar 

 in form). Night Monkeys may spread some odoriferous substance on 

 the branches that they rub against. But I have never seen a Night 

 Monkey smell or sniff at the Rubbing site of another individual in 

 an unusually attentive manner. 



The Rubbing by the individual with its mate and young appeared 

 to be a "triumph ceremony," proclaiming the successful defense of 

 its territory, in much the same way as some Resonant Grunt per- 

 formances. 



