This rat is recorded in the mountains of western Sumatra. The adult male type described in 1916 had dark-tipped back spines and a tawny patch on its chest.
The 1916 description says the adult male had spiny back fur with dark tips showing and an ochre-tawny patch on the chest.
A 2012 Mount Singgalang survey reported captures identified at the time as Niviventer rapit in heavily and slightly disturbed forest, but not in its undisturbed site. Later taxonomy assigns Sumatran populations from the N. rapit complex to N. fraternus, although the older paper gives no specimen-level re-identifications. Another survey recorded 42 N. fraternus on Mount Singgalang in 2018.
An extinction-risk assessment has not been added yet.