This rat was recorded in the mountains of western New Guinea. A 1979 survey reported specimens under the former name Rattus niobe haymani; the current MDD lists that name and the combination R. niobe arrogans as synonyms of Rattus arrogans.
The 37 Mount Karstens specimens identified then as R. niobe haymani were described as darker than two Mount Wilhelmina specimens then classified as R. niobe arrogans. MDD now lists both names under Rattus arrogans.
The 1973 survey recorded 37 specimens under the old name R. niobe haymani at 2,400–3,400 m on Mount Karstens. Reported sites included lower montane forest, fallen-tree and moss cover, forest openings, and lower alpine meadows.
An extinction-risk assessment has not been added yet.