A viscacha is a large South American rodent that belongs to the same family as chinchillas. There are two distinct types: mountain viscachas, which live on rocky slopes high in the Andes, and the plains viscacha, which digs massive underground burrow systems in the grasslands of Argentina. Despite looking somewhat like a rabbit or a large chinchilla, viscachas are more closely related to guinea pigs and degus.
Mountain vs. Plains: Two Very Different Animals
The word “viscacha” actually covers two separate groups of animals within the family Chinchillidae. Mountain viscachas (genus Lagidium) include several species that live at elevations between 3,000 and 5,100 meters in Peru, Bolivia, Chile, and the Argentine Andes. They shelter in crevices between rocks, much like their close relatives the chinchillas, and have fine, soft fur suited to frigid mountain conditions.
The plains viscacha is a single species and a very different animal. It lives at lower elevations in the grasslands and scrublands of Argentina, where it builds elaborate underground burrow networks called viscacheras. Where mountain viscachas are slim and agile rock-climbers, the plains viscacha is stockier and built for digging, with three powerful clawed hind toes compared to the mountain viscacha’s four relatively weak ones.
What a Viscacha Looks Like
Plains viscachas weigh between 2 and 8 kilograms, with males sometimes four times as massive as females. They have large, blunt heads with striking black and white facial stripes, and both sexes sport prominent mustache-like whiskers that are especially exaggerated in males. Their fur color matches their environment: light brown in sandy regions, dark grey where the soil is darker, with a white belly and coarse dark guard hairs running along the back. The tail is fully furred.
Mountain viscachas are smaller and more lightly built, with longer, curled tails and the dense, soft fur characteristic of the chinchilla family. Their large ears and big eyes give them a rabbit-like appearance that has made them popular subjects of wildlife photography, particularly in images where they seem to be lounging on sun-warmed rocks.
Burrows That Last Decades
Plains viscachas are highly social and live in colonies centered around their viscacheras. A typical group includes one to three adult males and two to four times as many females, plus their young. In the semi-arid scrub of La Pampa province, principal viscacheras contain anywhere from 18 to 93 individual burrows, with smaller satellite burrows scattered nearby. Every animal in the group has access to every burrow.
These burrow complexes can persist for remarkably long periods. One viscachera was documented as being in continuous use for 70 years. The overall layout, with clusters of principal and satellite burrows spread across a patch of land, resembles the “ward” structure seen in black-tailed prairie dog colonies. Plains viscachas also have a curious habit of collecting objects like sticks, dried dung, and bones and placing them near the entrances to their burrows.
Mountain viscachas, by contrast, don’t dig at all. They form communal dens in natural rock crevices, relying on the Andes’ endless supply of broken terrain for shelter.
Diet and Feeding
Both types of viscacha are herbivores. Mountain viscachas concentrate their diet on a few key grasses, with species like Stipa, Poa, and Festuca making up the bulk of what they eat. During winter, when food is scarcer and lower in nutritional quality, their diet narrows further, dominated by whatever hardy grasses remain available near rocky outcrops. They will travel some distance from their shelter to reach preferred grasses, even heavily browsing species that don’t grow abundantly in their immediate surroundings.
Plains viscachas graze on the grasses and low vegetation of their grassland and scrubland habitats, feeding primarily at night.
Reproduction and Lifespan
The two groups differ noticeably in their reproductive patterns. Mountain viscachas have a gestation period of about 140 days and typically produce just one offspring per litter. Plains viscachas carry their young slightly longer, around 154 days, but average two per litter, with as many as four possible.
Lifespan also varies. Mountain viscachas live roughly 3 years in the wild, though captive individuals have reached 19 years. Plains viscachas fare better in the wild, typically living 7 to 8 years, though their recorded captive lifespan tops out at just over 9 years, an unusual case where the wild lifespan nearly matches captivity.
Surviving Thin Mountain Air
Mountain viscachas live at altitudes where the available oxygen drops below 70% of sea-level concentrations. Animals that thrive in these conditions over generations develop a suite of adaptations to compensate. High-altitude species generally show increased lung volume and greater numbers of air sacs in the lungs, which together expand the surface area where oxygen passes into the bloodstream. Their cardiovascular systems remodel to move oxygen more efficiently, and their tissues adapt to extract more energy from less oxygen. Related high-altitude rodents like guinea pigs, which share the viscacha’s family tree, show exactly these kinds of changes.
Conservation Status
Viscachas are not currently considered threatened. Both the southern mountain viscacha and the northern mountain viscacha are classified as Least Concern on the IUCN Red List. Plains viscachas remain abundant across their range in Argentina, where they are sometimes considered agricultural pests because their extensive burrow systems can damage pastureland. Mountain viscachas face more localized pressures: their narrow, potentially fragmented range in the high Andes makes them vulnerable to habitat disruption, and they are a primary prey species for the endangered Andean cat.