The reddish-backed Thomasomys occurs in montane forests of northwestern Peru. Some specimens were collected on the ground, but detailed ecological records remain sparse.
The back is strongly rufous and the underside whitish. A small orange pectoral streak is described in the account.
Ground records come from tall shrub habitat, montane secondary forest, bamboo forest near a stream, and cloud forest. A brief observation of one animal described it as a good climber.
An extinction-risk assessment has not been added yet.