Wied's marmoset is a diurnal small monkey that lives in the coastal evergreen forests of eastern Brazil. Body length is 20–30 cm, weight about 350–400 g, and the tail is long at about 30 cm. It primarily eats fruit, flowers, nectar, tree sap, and small animals, and moves by clinging to trees and leaping. Groups consist of 5–9 individuals with multiple males and females, and breeding is often limited to a single dominant female within the group; twins are usually born. Gestation is about 4.5 months; young are weaned at 4–6 months and reach sexual maturity at 12–15 months. Populations have declined due to forest loss and fragmentation and capture for the pet trade, and it is listed as Near Threatened.