Based on a specimen collected at Maipures, near the mouth of the Río Tomo on the Río Orinoco, Defler and Bueno (2007) indicated that the night monkeys of eastern central Colombia north of the Río Guaviare are probably A. brumbacki.

Hershkovitz (1983) proposed that A. trivirgatus was the form in Colombia between the Rios Vaupés and Inirida, but Defler (2003, 2004) indicated that A. vociferans occurred in this region and that A. trivirgatus as such is restricted to the east of the Ríos Negro, lower Guainia, and Atabapo and, below the mouth the Río Atabapo, the Río Orinoco. To the north, in Venezuela, A. trivirgatus occurs south of the Río Orinoco and east as far the middle Rio Caroni. The extension east beyond the Río Caura is based on just one locality on the upper Caroni (Bodini and Pérez-Hernandez 1987; Linares 1998). A. trivrigatus is confined to north (left bank) of the Rio Negro to its mouth, extending east, north of the Rio Amazonas, as far as the Rio Trombetas. North it reaches the Serra da Pacaraima, but does not it seem extend into Guyana. In the state of Roraima, the Rio Mucajaí is indicated (by Hershkovitz (1983) as marking its northern limits.