Marmosets inhabit the rainforests of north-east and central Brazil. Preferred habitat is tropical rainforest, however, common marmosets are known to be highly adaptable, surviving in a wide variety of forest habitats. Family groups will maintain territories of 2-5 hectares. Marmosets have a flattened black face, thick white tufts on their ears, and long black and white fur. The tail is white ringed with black. Except for the big toes, a marmoset has claws not nails, unlike most monkeys.
Marmosets give birth to multiple offspring, with litter sizes of between 1 and 4. From birth, they have a very strong cling reflex and do not voluntarily leave their carrier’s back for the first 2 weeks of life. In the second week, the young become very active, crawling on their carrier’s back and investigating their surroundings. In the wild, they exhibit a high degree of birth seasonality, with two birthing peaks observed annually (April, May and June as well as September, October and November). This timing coincides with the maximum availability of food. Their mating systems are highly variable and can include monogamy (one partner at any one time), polygyny (2 or more female partners at one time) and occasionally polyandry (2 or more male partners at one time).
Marmosets are highly active, living in the upper canopy of forest trees. They live in family groups of 3-15, consisting of 1-2 breeding females, an unrelated male, their offspring and occasionally, extended family members and unrelated individuals. They are characterised by a high degree of cooperative care of the young and some food sharing and tolerated theft. Adult males, females (other than the mother), and older offspring participate in carrying infants. Most groups scent mark and defend the edges of their ranges, but it is unclear if they are truly territorial, as group home ranges greatly overlap.
Common marmosets have a wide and varied diet in the wild. Rainforest fruits, insects, lizards, small birds and eggs are all consumed, accounting for 24-30% of their foraging time. During seasonal fruit shortage, gum feeding becomes an important high-energy food supplement to maintain body health. They have long lower incisors which allow them to chew holes in tree trunks and branches to harvest the gum inside.