They are medium to large-sized rodents, weighing from 800 g (28 oz) to 8 kg (18 lb), with strong hind legs and large ears and a bushy tail.

They have large eyes, medium-sized ears, soft dense fur and short bushy tails.

Mountain viscachas and chinchillas live in craggy upland regions where they inhabit crevices among rocks and are skilled climbers.

[4][5] The plains viscacha is rated as being of "least concern" as it seems tolerant of habitat disturbance and although some populations have been eliminated locally through pest control measures and hunting, others have expanded into newly cleared areas.

[6] Both the northern and southern mountain viscachas are also considered of "least concern" as they have a wide range and are locally abundant in some areas.