Like many primates, Geoffroy’s marmoset is a gregarious, social animal, and typically lives in family groups of eight to ten individuals, consisting of the dominant female, her mate and their offspring, with breeding usually restricted to the dominant pair (2) (5) (6). Young remain within a group, even when adult, and help care for their siblings. These ‘helpers’ gain valuable breeding experience, which may be used when suitable habitat becomes available for them to establish their own territory, as part of a dominant, monogamous breeding pair (5). Dominance is enforced by scent-marking, scolding, cuffing and eye command. This is accentuated in the female by pheromones produced in her scent glands, which inhibit ovulation in subordinate females, preventing them from breeding as long as they remain within the group (6). The dominant female typically gives birth to twins, although singletons and triplets also occur, after a gestation period of around 140 to 148 days (2) (5) (6). The father carries the young, which are completely dependent for the first two weeks (5) (6). After this, all members of the group take turns in carrying. Infants are weaned and independent by five to six months, by which time they are capable of collecting their own food (6). Sexual maturity is reached at about 15 to 18 months of age (6), and individuals live around 10 years (5).
These diurnal, arboreal animals spend the day roaming around territories that may be up to 5 hectares in size, and sleep at night in tree holes or other shelters. Home ranges are overlapping and, although they are not defended, they are marked using scent, which is often smeared around favourite gum holes in trees. The diet includes plant gums and saps, nectar, fruit, insects, invertebrates and other small animals (5). This species has also been known to follow swarms of army ants, which flush many organisms up towards the trees, making them available for the marmosets (8).