Theoretical models of species coexistence between desert mammals have generally been based on a combination of food and microhabitat selection by granivorous rodents. Although these models are applicable in various deserts of the world, they cannot explain resource use by mammals in Neotropical deserts. The present study examines diet composition in a mammal assemblage in the Monte desert, Argentina. The results show that two main strategies are used by these mammals: medium‐sized species (hystricognath rodents: Dolichotis patagonum, Lagostomus maximus, Microcavia australis and Galea musteloides; and an exotic lagomorph: Lepus europaeus) are herbivores, whereas small‐sized species (a marsupial: Thylamys pusillus; and sigmodontine rodents: Graomys griseoflavus, Akodon molinae, Calomys musculinus, Eligmodontia typus) are omnivorous. Small mammals also show a tendency towards granivory (C. musculinus), insectivory (A. molinae and T. pusillus) and folivory (G. griseoflavus).

Food storage is an important adaptation of several animal species to the temporally variable or unpredictable food supplies that are typical of desert environments. In the present study, whether Eligmodontia typus and Graomys griseoflavus inhabiting sand dunes in the Monte desert displayed scatter-hoarding was investigated. Both rodent species prepared surface caches by digging small holes (1-3 cm deep) in the soil. Caches were partially covered with sand and dry leaves, which meant that all of the cache sites at each station could be found. Most caches were found below shrubs, that is, in a sheltered microhabitat rather than near the food source. The mean distance between caches and seed sources was significantly higher than the mean distance from food sources to shrubs. The proportion of caches was significantly higher in shrubs with high safety cover. The adaptive significance of this foraging behaviour could be a competitive tactic for the rapid sequestering of food from a rich and ephemeral source. Such behaviour would reflect predation risk, which constitutes an important foraging cost in deserts, and could also influence plant community dynamics.

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In desert areas, predation risk is one of the highest costs of foraging and is a major influence on animal behaviour. Several strategies are used by foragers for surviving and reproducing in desert areas. The foraging strategies of the small mammals of South American deserts are still poorly known. In this study, we investigated the foraging strategies of rodents of the Monte Desert in response to distance from seed sources to sheltered sites (i.e. shrubs) during two different seasons (wet and dry). We evaluated the relative rates of removal of two species of seeds (millet and sunflower) by rodents at two sites by establishing 80 seed sources, 40 in unsheltered microhabitats and 40 in sheltered microhabitats. We recorded both the number of caches and seed consumption for each source. We found that plant cover affected the foraging activity of rodents of the sand dunes in the Monte Desert because both consumption and numbers of caches constructed from sheltered seed sources were higher than those from unsheltered ones. Consumption of sunflower was higher in the wet season than it was in the dry season, when millet consumption increased. Sunflower was the preferred seed both from sheltered or unsheltered sources. We discuss the possible causes of the different foraging strategies used by rodents of the Monte Desert.