The black-mantled tamarin, Saguinus nigricollis, is a species of tamarin from the northwestern Amazon in far western Brazil, southeastern Colombia and northeastern Peru. It has often included the Graells's tamarin as a subspecies (in which case the distribution extends into eastern Ecuador),[3] but differs from that species in having reddish-orange rump and thighs.[4] The two are often said to be sympatric in Colombia (a major argument for treating them as separate species), though the accuracy of such reports has been questioned.[5] The body length is 15–28 cm.