64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



their fathers most of the time when they were not actually being 

 suckled by their mothers. The third infant was certainly carried 

 by its father much of the time, but I could not determine exactly how 

 much, simply because the father and mother were very difficult to tell 

 apart (without catching them in the hand). This was the infant that 

 was observed most frequently. It was first seen being carried by the 

 father at the age of 9 days. This was also the first time that it was 

 seen riding on the back of a parent. (It seems probable that these two 

 developments were causally related. But carrying on the back is not 

 a purely masculine pattern. The same infant sometimes rode on its 

 mother's back before and/or after being suckled.) I was informed 

 by a keeper at the National Zoological Park that a baby Night Monkey 

 born to a captive pair there, and raised by its parents, also usually 

 was carried by the father. 



This parental behavior is interesting from a comparative point 

 of view. Infants and young apparently are always carried by their 

 mothers, as long as they are carried at all, in such genera of New 

 World primates as Aloiiatta and Ateles (Carpenter, 1934 and 1935). 

 The only other platyrrhines in which the father is known to carry 

 the young regularly are the marmosets and tamarins (Sanderson, 

 op. cit., and Hill, 1957). 



There is at least one published record of a male Titi Monkey, Calli- 

 cehus, carrying young (L. E. Miller, quoted in Allen, 1916) ; but it 

 is not known if the habit is regular in the species. 



Hill's (1960) statement that Allen (in the same paper) cited evi- 

 dence to show that male Saimiri frequently carry young is appar- 

 ently erroneous. 



The carrying of young by males may be primitive among Platyr- 

 rhine and/or an indication of close phylogenetic relationship between 

 Night Monkeys and marmosets and tamarins. (Night Monkeys re- 

 semble marmosets and tamarins in a number of other characteristics.) 

 In any case, such behavior must be adaptive. Its principal advantage 

 may be the sharing of labor. When the male carries the young 

 part of the time, neither parent will become as exhausted and "run- 

 down" (and therefore susceptible to predators and disease) as the 

 female would be likely to become if she did all the work herself. (Even 

 if the male has the harder job because he carries the young most of 

 the time, he can support the strain better than his mate simply because 

 he does not have to produce milk. Males may get less tired also because 

 they are usually, or perhaps always, slightly larger and more powerful 

 than their mates.) 



