We compared the use of artificial food patches (giving-up density GUD technique) by small- granivorous mammals between forest interior and forest-pasture edge, strata (ground and understory), and across different moon illumination occurrence in a small, oak forest frag- ment in the Colombian Andes. Foraging costs for small mammals were higher near the edge than in the interior on the ground, but not at the understory. Small mammals preferred foraging on the ground than at the understory. Moon illumination had no effect. Our results indicate that forest destruction and its associated edge effect may reduce the area available for small mammals, consequently may affect the biotic interactions and the dynamics of Andean forest remnants, and this effect is modulated by the forest's vertical heterogeneity. Therefore, the use of behavioral indicators such as the food patch use, measured with the GUD technique, is an effective method to measure responses of Andean small granivorous mammals to human alterations.