58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



a female briefly before mounting and performing an apparently 

 successful copulation; but he will almost certainly not copulate suc- 

 cessfully, or at least will not copulate successfully immediately after 

 the Allogrooming, if he grooms her vigorously for more than a few 

 seconds. 



This would suggest that the performance of prolonged Allogroom- 

 ing tends to "consume" an appreciable amount of copulatory motiva- 

 tion, i.e., raises the releasing threshold of overt copulatory behavior 

 in at least many circumstances. 



Allogrooming may have several functions. Its successful per- 

 formance may help to reduce the actual or potential hostility between 

 male and female. The close physical contact involved may also pro- 

 vide some direct sexual stimulation. 



Either one or both of these effects may be very rapid. They may 

 be more rapid but less long sustained and/or have less potential 

 strength than the effect of raising the threshold for copulatory be- 

 havior. If there are such differences in speed, and possibly strength, 

 between the contradictory effects of Allogrooming, this would ex- 

 plain why successful copulations frequently follow brief grooming 

 and rarely follow prolonged grooming. 



Repeated Allogrooming may also have the relatively very long-term 

 effect of strengthening the pair bonds between mates. 



If the Allogrooming of Night Monkeys does function in these 

 different ways, it is basically similar to many "precopulatory" patterns 

 of other species, e.g., the Allogrooming of many other mammals and 

 the Food-begging and Allopreening of many birds. 



The penis of a male Night Monkey may be erected before he mounts 

 during copulation, but it is not "shown off" to the female. This 

 behavior pattern does not seem to be a ritualized display like the 

 penile erection of Squirrel Monkeys, Saimiri, described by Ploog 

 and MacLean (1963). 



The only other patterns which must be considered in connection 

 with the sexual behavior of Night Monkeys are Squeak notes. These 

 seem to be typical of young animals and infants, but are uttered also 

 by adults in certain circumstances. 



Many of the Squeaks uttered by adults may be reversions to, or 

 persistent remnants of, juvenile behavior; and may be produced by 

 some or all of the same wide range of causes as the Squeaks of 

 juveniles (see below). Squeaks are certainly uttered more frequently 

 by adult individuals that have been raised in complete or partial isola- 

 tion from other individuals of their own species than by adults raised 

 in the wild under natural conditions; and the retention of juvenile 



