The golden-headed lion tamarin lives within group sizes ranging from 2 to 11 individuals, with the average size ranging from 4 to 7.[4] According to various sources, the group may consist of two adult males, one adult female, and any immature individuals,[5] one male and one female and any immature individuals,[6] or there may be one producing pair and a varying number of other group members, usually offspring from previous generations.[7][8] There is not much known on its mating system, but according to different sources, and information on the possible social groups, it can be assumed that some may practice monogamous mating systems,[6] and some may practice polyandrous mating systems.[5] Both males and females invest energy in caring for the young,[6] and all members of the group also help with juvenile care.[7][8]