Known for their luxuriously thick fur, these cuddly-looking, rabbit-like animals range in head-and-body length from 11.8 to 23.6 inches (30 to 60 centimeters) and can weigh from 1.1 to 19.8 pounds (0.5 to 9 kilograms). Females are usually larger than males. The animals’ fur, which vary in color from brown to bluish gray to pearly white, have a uniform, soft underfur. The chinchillas and mountain viscacha have especially fine, silky fur, as well as special bristles on their back feet to groom themselves. As many as sixty hairs can grow out of one hair follicle. All the species have bushy tails. Viscachas are generally larger than chinchillas, while chinchillas have much larger ears and longer tails relative to their size. All of the species have broad, large heads, thick necks, and strong feet and rear legs. With its distinctive black-and-white facial pattern, the plains viscacha is unique among the family. Depending on their native environment, some of the animals are adapted to jumping, while others have evolved to burrow. The pads of their feet are hairless, and front feet are usually shorter than the back feet, which are long and bony. The four digits on their front feet are dexterous and useful in manipulating food. Their cheek teeth grow continuously and must be worn down regularly. The pupils of their eyes are cat-like, with vertical slits.


This family of mammals occurs only in western and southern South America, but their largest populations are in southern Peru, Argentina, Bolivia, and northern Chile to the foothills of the Andes Mountains in Patagonia (Argentina).


While most of the viscacha species tend to remain at elevations below 1,640 feet (500 meters), the mountain viscacha and chinchillas colonize areas from 13,120 to 16,400 feet (4,000 to 5,000 meters). The plains viscacha lives in grasslands with sparse vegetation, but all the other species seek out rocky areas where they can dig their burrows and hide from numerous predators.


Chinchillids (members of the Chinchillidae family) are mainly herbivores, plant eaters, and live on seeds and grass, although those species endemic at higher elevations also eat mosses and lichens. All species occasionally eat insects as well.


The mountain viscacha and all the chinchillas eat, sunbathe, and groom while sitting erect on their hindquarters. The plains viscacha and all the chinchillas look for food at sunset and throughout the night, but the mountain viscacha is alert and active by day and hides by night. All of these animals live in colonies of some sort, but some are more tightly knit and structured than others. For instance, the plains viscacha is compelled to use a communal burrow system, and the colony is dominated by a strong male and an assistant he chooses from the fifteen to thirty members of the family group. On the other hand, chinchillas and mountain viscachas have a more relaxed social structure in which the colony is more spread out and can consist of from four up to 300 animals, with different burrows housing individual family groups. As colonial animals, there is always at least one individual on guard to watch for predators and other dangers. The mountain viscacha has a warning call that sounds like a high whistle, whereas the plains viscachas have a more varied palette of sounds, including a characteristic “uh-huh” sound, numerous whines, and their own species-specific warning calls. All six species have been observed taking dust baths and engaging in play chases, and all but the plains viscacha are amazingly agile as they jump among rocky outcroppings.

Female chinchillids are very aggressive to other females and even many males, with much growling, teeth chattering, and urinating, although there are rarely serious fights in the wild. They have unusually long gestation periods for rodents of their size, carrying their young 90 to 154 days before giving birth to one to six pups. The average female, which reaches sexual maturity (able to mate) at from eight to fifteen months, can produce one to three litters every year. Pups are born with open eyes and are fully furred, and their mothers nurse them for six to eight weeks. This species usually has more than one mating partner during the breeding season.


All species in this family, but especially the chinchillas, have been intensively harvested and farmed commercially for their valuable fur as well as for their meat. Their pelts are still the most expensive in the world. Plains viscachas are considered a pest and are destroyed in large numbers in many areas because their foraging leaves large swaths of bare ground (ten of them are rumored to eat as much as a sheep daily) and their burrows cause many cows and horses to break legs when they accidentally step into them.


Due to overharvesting, the long-tailed chinchilla is listed as Vulnerable, facing a high risk of extinction, by the World Conservation Union (IUCN), while the short-tailed chinchilla is Critically Endangered, facing an extremely high risk of extinction. The animals are now protected by law in their native habitats, although this is of limited benefit due to their remote habitats. Conservation groups have attempted to reintroduce chinchillas to Andean habitats, but with no success so far.