The tympanic annulus may be present, reduced, or absent; the right and left side of a single individual may show different state.

The dorsum has either uniform color or subtle mottling or indistinct spots; the former is more typical.

[4] Telmatobius niger has been recorded in the vicinity of streams and rivers in cloud forests, moist scrubland, high-altitude páramo grassland, evergreen montane forests, and dry montane scrubland at elevations of 2,469–4,000 m (8,100–13,123 ft) above sea level.

During daytime, adults usually occur beneath rocks and in weedy vegetation in and at the edge of streams.

The possible reasons for the decline include disease and parasites (e.g., chytridiomycosis), abnormal climatic conditions, and habitat destruction and degradation caused by agricultural development and human settlement.