Young (3-4 years old) laboratory-reared rhesus monkeys were observed in five 15-minute tests with 1-15-day-old infants. Males and females were equally likely to investigate infants. Females communicated more with infants by grin-lipsmacking and gurgling-gestures that were not shown by any males. More females presented the ventrum to infants than did males. Females contacted infants more than did males by grooming, crouching over, and having full body contact with them. To see whether prenatal androgens produced the male pattern of response, we conducted similar tests with pseudohermaphrodites (prenatally androgenized genetic females) and neonatally castrated males. On most sexually dimorphic behaviors, pseudohermaphrodites behaved more like females than like males. Castrated males, like females and pseudohermaphrodites, crouched over infants more than did intact males. Castrated males differed from females only on one infant-directed response, the grin-lipsmack. These comparisons showed that defeminization of the repertoire of infant-directed responses was measurable only in intact males. We conclude accordingly that prenatal androgens alone are not responsible for defeminization of this repertoire and that a contribution from postnatal androgens is likely to be necessary.
To determine whether pregnancy influences the response of rhesus monkeys towards infants, 11 females were observed during 15-min exposures to a 1- to 15-day-old infant at 1- to 2-week intervals throughout pregnancy. No evidence was found for increasing willingness to contact infants as pregnancy progressed. The parturition of 5 of these females was observed, which included 1 live breech birth. These primiparae all established ventral contact with their infants at birth, though most of them appeared to passively allow the infant to initiate contact while their own attention was directed at licking the birth fluids.
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