It occurs in marshy steppe wetlands, where there are large patches of dense and tall (c.2 m) rushbeds Schoenoplectus (Scirpus) californicus, usually surrounded by wet meadows with lush green grass, and associated with a permanent water body, such as a river, stream or lake (Mazar Barnett et al. 1998, A. Jaramillo in litt. 2000, Imberti and Mazar Barnett 2003, Mazar Barnett et al. 2014). It appears to leave sites with less favourable habitat during the winter, and some northerly post-breeding dispersal or possibly partial migration may occur, at least in southern populations (Mazar Barnett et al. 1998, 2014).

Rallus antarcticus is known from southern Chile and Argentina. It is thought to have populations in five geographically distinct areas: 1) the Magellanic steppe south of the Gallegos River and Coyle River Basins; 2) the transitional region of the Torres del Paine and Glaciares National Parks; 3) around Gobernador Gregores, along the Chico River Basin; 4) the Deseado River Basin; and 5) along a coastal axis in north-eastern Patagonia (Mazar Barnett et al. 2014). The species has been recorded historically in Tierra del Fuego, Buenos Aires, and Rio Negro, Santa Cruz and Chubut in Argentina, and in Valparaiso, Santiago, Colchagua, Llanquihue and Magallanes in Chile. It was previously known from just a few specimens and sight records, and since 1959, there were no documented records until the species was rediscovered in 1998, at Estancia La Angostura, Santa Cruz, Argentina (Mazar Barnett et al. 1998). Further fieldwork in 1998-2006 recorded the species at a total of 21 localities in in Santa Cruz, Chubut, Buenos Aires and Rio Negro, Argentina, and in Magallanes (XII Region), Chile (Imberti and Mazar Barnett 1999, Imberti and Mazar Barnett 2003, Pugnali et al. 2004, Soave et al. 2009, Mazar Barnett et al. 2014). Surveys in Santa Cruz in 2009-2013 detected the species at two more localities (Roesler et al. 2014). Records from Buenos Aires, Rio Negro and the Valdes Peninsula were made outside the breeding season and may have represented migratory or vagrant individuals (Mazar Barnett et al. 1998, Pugnali et al. 2004, Mazar Barnett et al. 2014).  A record from the Falkland Islands (Malvinas) is likely to have been a vagrant individual, suggesting a tendency to undergo long-distance movements (Pugnali et al. 2004). All recent records fall outside the historical range, suggesting a large range contraction (J. Mazar Barnett in litt. 2000, 2003). Nesting has been confirmed only in Torres del Paine National Park, Chile (Matus et al. 2017) and in a locality adjacent to Los Glaciares National Park in Argentina (Moroni and Salvador 2016).

Conservation Actions Underway
The species is listed as nationally Endangered in Argentina (MAyDS and Aves Argentinas 2017). It occurs in several protected areas including Torres del Paine, Pali Aike and Los Glaciares National Parks, Bosques Petrificados Natural Monument, Península Valdés and Laguna Nimez (Imberti and Mazar Barnett 1999, A. Jaramillo in litt. 2000, Imberti and Mazar Barnett 2003, Mazar Barnett et al. 2014, S. Imberti in litt. 2020).

Extensive mink control has taken place in the Buenos Aires Lake Plateau area, and there were plans to expand control efforts into the lowlands where they may benefit the rail (Fasola and Roesler 2016). At La Angostura, a portion of the wetland is managed to protect rails to support birdwatching tourism (de Miguel et al. 2019).

Conservation Actions Proposed
Survey historic localities, particularly in Chile (Mazar Barnett et al. 2014). Carry out surveys across the known range to gain a better estimate of the population size and trends. Research the species's movements to better understand seasonal movements and subpopulation structure. 

Create further protected areas at key sites such as El Zurdo and Bella Vista Bitsch (Mazar Barnett et al. 2014). Manage and legally regulate grazing around known populations to prevent overgrazing (Imberti and Mazar Barnett 2003). Encourage landowners to preserve wetland areas during burning (de Miguel et al. 2019). Prevent overgrazing of habitat at protected sites where the species occurs. Regulate the abstraction of water from wetland sites (Imberti and Mazar Barnett 2003). Ensure that agricultural development has minimal effects. Advocate against the construction of dams that are likely to negatively affect the species's habitat, and advocate for modifications that will reduce their impact on habitat (A. de Miguel, I. Roesler and L. Fasola in litt. 2018). Control mink around localities where the rail is known to occur. Raise awareness of the species and potential threats among landowners and school pupils.