Wied's marmoset (Callithrix kuhlii), also known as Wied's black-tufted-ear marmoset, is a New World monkey that lives in tropical and subtropical forests of eastern Brazil. Unlike other marmosets, Wied's marmoset lives in groups consisting of 4 or 5 females and 2 or 3 males (plus children). They are matriarchal, and only the dominant female is allowed to mate.