Four breeding females in a free-ranging group of buffy-headed marmosets (Callithrix flaviceps).

The reproductive patterns recorded in a free-ranging group of Callithrix flaviceps were unique in a number of ways, including 4 females breeding simultaneously, a non-breeding dominant female, and a well-defined birth season. In addition, all observed copulations involved extragroup individuals. The more socially dominant breeding female had more births and more surviving offspring, on average, than subordinate females, and was implicated in at least 1 infanticide. All 4 females carried their own infants for relatively long periods following the births, apparently as a defence mechanism related to the risk of infanticide. It remains unclear whether the unusual number of breeding females in the group represents a species-specific pattern, or the result of specific local circumstances.