The responses of small mammal communities to forest disturbance by logging were evaluated. The study area was located in the Imataca Forest Reserve (Venezuelan Guayana Region), where vegetation was predominantly lowland rain forest. Field analyses were based on a comparative inventory of species inhabiting primary forests and areas disturbed by selective logging. The taxonomic groups used as indicators of the ecological impact of logging belonged to the orders Didelphimorphia, Chiroptera, and Rodentia (families Sciuridae, Muridae, and Echimyidae). The following sampling methods were used: (1) mist nets; (2) traps in 2.4 ha grids (each with 120 stations: 60 at ground level and 60 in trees); and (3) diurnal and nocturnal sight surveys. Total sampling effort consisted of 1904 net-hours, 10,320 trap-nights, and 567 h of direct observations. At least 83 mammalian species inhabited the evaluated forests (74.7 percent corresponding to Chiroptera), of which 15.3 percent were restricted to primary forest. In logged areas, small mammal communities were characterized by: (1) higher abundances of individuals; (2) lower proportions of carnivorous and gleaning insectivorous bats; (3) increases in the relative abundance of frugivorous bat species that eat the fruits of colonizing plants; (4) higher proportions of aerial insectivores (Molossidae) at the lowest levels of the forest; (5) simplification in trophic structure of non-volant species, with semiarboreal predator-omnivores being the dominant guild (followed by terrestrial frugivore-omnivores); and (6) reduction in the relative abundance of mainly canopy-associated species. These results are explained by: (1) lower availability of key resources associated with primary forest (e.g., roosts in hollow trunks of mature trees, canopy fruits, and tree-crown continuity); (2) higher relative abundance of some food resources, such as terrestrial invertebrates and saprophytic plants, principally in areas where primary production is limited by low-fertility soils; (3) increase of roosting sites under fallen trunks; (4) modification of microclimatic conditions at the understory level as a consequence of a greater incident sunlight after canopy opening; and (5) increase in density of early successional plants. The implications of these results to the conservation of biodiversity in forests managed for timber extraction in the Venezuelan Guayana Region are discussed.
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Vol. 32 • No. 1