Adults weigh about 500-800 grams with females larger than males. Large, rounded ears and eyes, pupils vertical slits. The short forefoot and narrow hind foot have four digits with stiff bristles surrounding the weak claws.
Tails have coarse long gray and black hairs on the dorsal surface.
Relatively barren foothills of the Andes at elevations of 3,000 to 5,000 meters and in the coastal mountains of Chile, sheltering in crevices and holes among the rocks. Strictly herbivorous, eating any available vegetation. Colonial, formerly found in groups of about 100 individuals. Earlier reports of monogamy probably erroneous. Gives birth to two or three exceedingly precocial young weighing about 35 g. each.