The weight of an adult southern viscacha is about . They suggested the English common name of "Ecuadorean mountain viscacha". The plains viscacha should not be confused with the plains viscacha rat. The long-term social unit of the plains viscacha is the female group. They hunt the same prey, the mountain viscacha ("Lagidium viscacia"), a rodent. The plains viscacha is the largest species in its family. Plains viscacha rats are solitary, and nocturnal. The northern viscacha is common within suitable habitat in its range. The northern viscacha occurs in central and southern Peru and northern Chile. Members of the other genera are called viscacha rats. The northern viscacha is more often found on larger, steeper portions of cliffs. Viscacha rats are a group of rodents in the family Octodontidae. Mountain viscacha rats are nocturnal and solitary, spending the day sheltering in rock crevices. The viscacha looks much like a rabbit due to convergent evolution.