Patagonian opossum  (Lestodelphys halli)

Classified as Least Concern (LC) on the IUCN Red List (1).

Not only is the Patagonian opossum the only member of its genus, it is also the most southerly occurring marsupial in the world (3) (4). As an adaptation to life in a cold climate, its fur is short and fine, yet extremely dense, insulating the Patagonian opossum against the harsh prevailing conditions (4) (5). The relatively short tail, which may become swollen with fat, is also covered in a dense fur of short fine hairs (3) (6). This peculiar species is more adapted to a terrestrial and carnivorous lifestyle than other opossums in South America, with long canines, a short, broad muzzle, strong, robust legs and elongated claws (3) (4). The upperparts are dark greyish-brown, with black eye rings and white cheek patches, and the underparts and legs are whitish (3) (5). Like other opossums, this species has well developed eyesight as well as long, touch sensitive whiskers and acute hearing. When threatened, it will warn the intruder of its aggressive nature by curling back its lips and opening the mouth to reveal rows of sharp teeth (6).

The Patagonian opossum is only found in southern and central Argentina, where it ranges from the province of Mendoza in the north, southwards to Santa Cruz and east to central Patagonia (1) (4) (7).

The Patagonian opossum inhabits treeless grasslands and shrublands on the Patagonian steppe (1) (7).

Inhabiting remote and often inhospitable areas, the Patagonian opossum is perhaps the least known opossum in the Americas, with virtually nothing known about its biology (3) (7). However, from the few studies of the species, and from the structure of its skull, feet and teeth, it is known to have a predominantly carnivorous diet, feeding upon mice, small birds and beetles of the family Tenebrionidae. This behaviour most likely evolved in response to the seasonal lack of insects and fruit in its barren habitat (3) (8). The Patagonian opossum is also thought to hibernate during winter, using the fat stores in its swollen tail as an energy reserve during this period (4) (5).

Due to its wide range, presumed large population, and the absence of any significant threats, the Patagonian opossum is not currently considered at risk of extinction (1). However, the Patagonian steppe is a unique, fragile environment vulnerable to disturbance and some opossum populations are threatened by agriculture and livestock encroaching upon grassland habitat (1) (9). Overgrazing by sheep is a particularly severe problem as the sheep reduce the cover of natural plants and expose the soil to erosion, leading to desertification, while grasslands may be burned to create space for farmland (9) (10).

While the Patagonian opossum is not the target of any known conservation efforts, there are a number of reserves within its range (1). The Conservation Land Trust is helping to protect one such area at El Rincón and hope to integrate it into the existing Perito Moreno National Park, while the Wildlife Conservation Society is working with local people to reduce the impact of livestock grazing upon natural habitats (10) (11). The Patagonian opossum will also benefit from recommended further surveys aiming to determine the full extent of its distribution (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out about the conservation of the Patagonian steppe, see:

• Wildlife Conservation Society:
  http://www.wcs.org/saving-wild-places/latin-america-and-the-caribbean/patagonia-and-southern-andean-steppe-argentina.aspx
• Conservation Land Trust:
  http://www.theconservationlandtrust.org/eng/pa_elrincon.htm