Patagonian mara are the third largest rodents in the world, the capybara (Hydrochoerus hydrochaeris) is the largest and the beaver (Castor sp.) is second largest. They have grey-brown fur and long, powerful rear legs. These legs make the Patagonian mara well adapted for running across their grassland habitat. They have several different ways of moving; from a slow rabbit-like hop to a high speed bouncing run.
Patagonian mara travel in mated pairs, which remain together for life. Each pair have a home range of around 40 hectares, which will overlap with the territories of other pairs. They do not appear territorial, but the male will follow his female guarding her against rival males and predatory animals. When particularly rich areas of food become available more than 70 individuals may gather in one place.
Each year a female will have two or three litters of one to three young. They are well developed at birth and quickly join the offspring of around 15 other mara pairs in a communal burrow. Parents will visit in turn to nurse their young, which they identify by scent.
The Patagonian mara prefers to eat grasses and herbs, but will eat other vegetation if grass is not available.
This species is classified as Near Threatened by the IUCN. The main threats facing them are hunting, habitat destruction for agriculture and competition for food with introduced species, such as sheep and European hares.