The southern Darwin's frog inhabits the temperate forests of southern Chile and Argentina, latitudinally from Concepción to Aysén. Although very similar in appearance to its northern congener, this species is fully adapted to terrestrial life within the native forest, requiring no bodies of water for any stage of its life cycle. This is possible because the neomely of the southern Darwin's frog is complete: the tadpoles reach metamorphosis inside the father's vocal sac, before being released into the forest as small frogs.

The southern Darwin's frog is an incredible animal, showing considerable latitudinal variation in colouration and size, although never exceeding 4 cm in length. In the more seasonal environments of the Andes mountain range, the frogs are larger and show a higher percentage of brown colouration, whereas in climatically more stable environments, such as Chiloé Island, these frogs are smaller and show a higher percentage of colouration in shades of green. Their ventral colouration is completely different from the dorsal side, interspersing black and white patches to form a pattern that is unique to each individual, much like a fingerprint.

Like the Sapito Vaquero, the southern Darwin's frog emits a whistle as a form of call. This call is used by males to attract females, but it appears that females also commonly emit this call themselves, suggesting that the call may have a social importance that goes beyond its use for reproductive purposes alone.

Populations of the southern Darwin's frog have also shown an alarming decline since the 1980s. Particularly concerning is the situation of the populations closest to Concepción, the great majority of which have disappeared. In addition to habitat loss, these frogs are highly susceptible to a fungal skin disease in amphibians known as chytridiomycosis. For these reasons, this species is classified as Threatened under Argentine law (Secretariat of Environment and Sustainable Development) and Endangered under Chilean law (Species Classification Regulation) and on the IUCN Red List.