Pygmy marmosets

Pygmy marmosets (genus Cebuella) are small New World monkeys. The genus consists of two species, the Western pygmy marmoset (Cebuella pygmaea), and the Eastern pygmy marmoset, (Cebuella niveiventris). The smallest monkeys in the world, at just over 100 g (3.5 oz), they are native to rainforests of the western Amazon Basin in South America. They are generally found in evergreen and river-edge forests and are gum-feeding specialists, or gummivores.

About 83% of pygmy marmosets live in stable troops of two to nine individuals, including a dominant male, a breeding female, and up to four successive litters of offspring. The modal size of a standard stable troop is six individuals. Although most groups consist of family members, some may also include one or two additional adult members. Members of the group communicate using a complex system including vocal, chemical, and visual signals. Three main calling signals depend on the distance the call needs to travel. These monkeys may also make visual displays when threatened or to show dominance. Chemical signaling using secretions from glands on the chest and genital area allow the female to indicate to the male when she is able to reproduce. The female gives birth to twins twice a year and the parental care is shared among the group.