The montane fish-eating rat lives beside Andean rivers and streams, where it searches for insects and other small prey from dusk into the night.
Its back is blackish gray and its underside is paler. Slight webbing occurs between some toes of the hind feet; together with its thick fur, this is described as a swimming adaptation.
It is active at twilight and night and spends most of its time on land. It feeds along streams on insects and spiders, but is described as less specialized for swimming than some related fish-eating rats.
An extinction-risk assessment has not been added yet.