Phylogenetic constraints and ecological factors have been suggested as alternative key factors in the evolution of animal sociality. The mara (Dolichotis patagonum) is a cavid rodent endemic to Argentina that has the particularity of being monogamous with a communal breeding system. Researches on reproductive behavior of mara in its natural habitat have been restricted to Peninsula de Valdés (PV). In this work, we studied the breeding behavior of the mara in Sierra de las Quijadas National Park (SQNP). A census to locate mara's dens in 230 ha, was conducted through adjacent line transects of five meters width. After locating the dens, we followed their reproductive activity using camera traps. A density of 4.34 randomly distributed dens/ha was found. No communal breeding was observed. Breeding season extended from October to June. Estimated density was from 0.16 to 0.24 reproductive adults/ha. The survival rate of juveniles was 31.3%. These observations differ from those reported for the species. Resource dispersion hypothesis could explain both reproductive strategies prevailing in the extremes of its distribution, SQNP (solitary breeding) and PV (communal breeding). The intraspecific variability registered enhances the importance of ecological factors in determining sociality traits for the mara.