Microhabitat Use by Small Mammals in Central Chile

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Abstract
Through field observations, field and laboratory experiments, I studied microhabitat use by small mammals inhabiting an evergreen shrubland in central Chile. Akodon longipilis, A. olivaceus, Marmosa elegans, Oryzomys longicaudatus, and Phyllotis darwini used areas under shrub canopies more frequently than openings between shrubs. Distribution of food resources, predation risk, and the density of the herb layer apparently combined to enforce this pattern. Shrub seeds, arthropods and predator refuges were more abundant in the underscrub than in the open. Small mammals responded to silhouettes of predators. Their few forays onto the open microhabitats ocurred only during dark nights of autumn and early winter. A dense cover of exotic herbs from late winter to summer hampered the movements of the small mammals. Food, predation, and microhabitat structure were the proximate factors shaping the selection of microhabitats, but human disturbance apparently was the ultimate factor. Disturbance: a) reduces shrub cover, leading to increased predation pressure as the extent of unprotected areas increases; b) creates a more patchily food distribution; and c) favors the invasion of exotic herbs into the openings.