Black-eared marmoset (Callithrix penicillata). A marmoset native to southeastern Brazil, inhabiting Atlantic forest and cerrado, with a strong gum-feeding (exudativorous) habit centered on tree sap. The lower incisors and canines are well developed for gnawing tree trunks to obtain sap. Head-body length is 20–30 cm, weight about 300–350 g. They form small multi-male multi-female groups of about six individuals. Gestation is about five months; they typically give birth to twins, and infant care is shared within the group. They are highly adaptable and currently listed as Least Concern, but population trends are decreasing.