Originally described from Manu National Park, Peru, A. macero is now known to occur widely throughout southern Peru, and extending into western Brazil in Acre state. This species is known from the lowlands up to approximately 1500 m elevation.
Adults were found to be near small streams during the end of the dry season, and presumably move out into the general forest during wetter times of the year. Tadpoles are thought to be deposited in streams as opposed to standing water.
This species has a large range, much of which is in a national park, and is therefore at minimal risk of population declines.
Sister to a clade containing A. rubriventris plus A. altamazonica.