9723842 French Among mammals, infant care is commonly limited to maternal care. However, in a small proportion of species, fathers and other group members contribute to the care and provisioning of dependent infants (paternal and alloparental care, respectively). Although we know much about the patterning of this care, little attention has been directed toward the underlying mechanisms that regulate the delivery of parental care by individuals other than the mother. The studies proposed will examine the physiological and experiential determinants of parental care in the black tufted-ear marmoset (Callithrix kuhli). In the marmoset, maternal effort is limited essentially to nursing, and adult males and older offspring provide the majority of care to dependent infants. Initial observations indicate that older sons and fathers living in family groups undergo breast elaboration in the presence of infants, suggesting an endocrine involvement in infant care by males. Through the use of unobtrusive behavioral observations and noninvasive urine sample collection, French will test the degree to which responsiveness to infants and levels of parental behavior are affected by gonadal steroids (estrogen, progesterone, and testosterone) and pituitary peptides (prolactin). The generality or specificity of the physiological responses to infants will be tested by comparing the endocrine responses of both marmosets and squirrel monkeys (a non-paternal species) to infant-associated stimuli. Further, the strength of the social attachment between male and female partners, assumed to be critical for the evolution of male parental care, will be tested by providing pairs with a variety of threats to the integrity of the pair (e.g., temporary separations, encounters with strangers). Together, these projects will provide insights into the mechanisms that control responsiveness to infants and adult social partners in a species characterized by high levels of male parenta l care and strong heterosexual relationships.
