The Mantled Giant Mastiff Bat is known from northeastern Papua New Guinea. A comparative account gives its ear length as 23–25 mm, and later sightings include both forested and urban areas.
A 1992 comparison reports ear lengths of 23–25 mm for O. secundus.
A 2015 dissertation summarizes sightings in both forested and urban areas. Its roost sites remain unknown.
An extinction-risk assessment has not been added yet.