The Sierra del Tontal chinchilla rat is thought to be primarily diurnal, being most active in the early morning, and live in groups of three to four individuals. They shelter in rocky crevices on east-facing slopes, and deposit their faeces in large latrines. They are herbivorous, and feed almost entirely on jarilla bushes, being resistant to the toxic compounds produced by those plants. Like the related Punta de Vacas chinchilla rat, the Sierra del Tontal species has a pair of false teeth in the mid-line of its palate, which apparently help with food manipulation and are aided by a horny pad on the tongue. These false teeth arise from the epithelium of the mouth, and are not preserved in skeletal remains of the animal.