Like other lion tamarins, golden-headed-lion tamarins are diurnal. They feed mainly on fruits, and play an important role in seed dispersal. They also feed on flowers and nectar (2), and prey on small animals such as frogs, snails, lizards and spiders, and may opportunistically feed on gums, saps and latex from trees (3) (5). Animal prey is found in the forest floor litter and in the trees, in holes and crevices, and by breaking rotting wood to find large insects (6) (8). Their long hands and slender fingers help with this method of foraging (3) (5).
These social monkeys live in small groups of about 2 – 11 individuals (average 5 – 8) in low densities of 0.5-1 group per km². There can be more than one adult male and female in the group but only one female actually breeds (7) (8). The other females' reproduction is suppressed by the behavioural domination by the reproductive female, and by the effects of her pheromones and genital gland scent (5). Males and other group members play a major role in caring for the young (9). The co-operative breeding system of callitrichids appears to be unique amongst primates, and serves to help the breeding female care for the offspring (6). Lactation and feeding the young demands a great deal of energy, and so males and other group members often carry the young, allowing the female more time to forage and feed, while other members of the group also help by surrendering food morsels to the young and breeding female (6). This explains why the female is usually larger in size than the male. In fact research suggests that smaller males are often preferred mating partners by the females as they are more nimble in the forest and therefore better food gatherers (5).
Like other callitrichids, this lion tamarin usually gives birth to twins (3) (7). Gestation period is 125-130 days (9), and the offspring are born 9 – 15 % of the mother's weight, which is considerably heavier than those of other primates. They are carried everywhere rather than being left in nests (7). Once established as breeders in a group, a female can produce twins once a year, and sometimes twice (7).