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The viscacha rat Octomys mimax is endemic to western Argentina; it inhabits lowland deserts and uses rocky crevices as resting sites. The aim of this study was to assess macrohabitat selection relative to the occurrence of rocky crevices and to evaluate seasonal variations in macrohabitats selected by this rodent in Ischigualasto Provincial Park, San Juan, Argentina. Random locations were classified as used or available based on signs recorded in rocky crevices. We confirmed the absence of the viscacha rat in macrohabitats with sandy or silty substrates. We provide new records of viscacha rat in creosote bush scrub, the most abundant macrohabitat of the Monte Desert. This result extends the known range of macrohabitat use for this species. The viscacha rat increased the number of rocky crevices used in the dry season, probably because the species increased its foraging area due to the low food resource abundance. Another possible reason is an increase in density due to new births and dispersal of young in this season. The present study highlights the importance of considering signs of presence for species with low capturability as well as of collecting data throughout multiple seasons for a better understanding of habitat selection and species distribution.