Females of both genera have four mammae. The species M. shiptoni and M. niata live in high mountains, but M. australis occurs throughout Argentina except in the humid northeastern provinces. It is the most abundant member of the Caviinae in the semiarid thornbush of central Argentina. In such habitat it uses clumps of thornbush for cover and makes runways through the open areas between clumps of bushes. Under the bushes it digs a shallow depression, in which it rests and sleeps, and it keeps the surrounding area clear.
Most activity is diurnal.
Microcavia sometimes climbs bushes and low trees to feed. The diet consists mostly of leaves and also includes fruits. Animals were never seen to drink and presumably got sufficient water from succulent vegetation. Population size in a given area varies substantially, depending on reproductive activity and movements. Mean home range was 7,720 sq meters for males and 3,525 sq meters for females.