Abstract
The behavior of a free-ranging group of buffy-headed marmosets (Callithrix flaviceps) was observed in detail over a five-month period following the birth of twins. Infant care, principally carrying and food sharing, were analyzed and the variation both between age-sex classes and through time investigated. Potentially reproductive males exhibited a relatively high degree of interest in the infants during the first week following birth, but their provision of care was otherwise little different from that of other group members. The data are considered in relation to the factors stimulating care-giving behavior and possible differences between callitrichid genera are discussed.