Nonvolant small mammals from a southwestern area of Brazilian Cerrado: diversity, habitat use, seasonality, and biogeography

Abstract

Introduction. The Cerrado is characterized by a mosaic of habitats ranging from open grasslands to dense arboreal savannas and woodlands, with gallery forests along watercourses. Extensive areas of Cerrado have been gradually deforested in the last 50 years, currently only 20% of the biome still retains its original vegetation, and only 2.5% is preserved as permanent protected areas. Scientifi c knowledge of the Cerrado fauna, such as composition, natural history, and geographic distribution of its species is very important to conservation strategies. Nevertheless, most of the Cerrado still remains poorly sampled and studied. Although an increasing number of works have been published for Cerrado nonvolant small mammals in recent years, there are few studies dealing with biogeographic patterns for the biome. The objective of this study was to investigate the diversity of nonvolant small mammals and to determine the habitat use of the species encountered at Emas National Park - ENP, one of the most important reserves of the Cerrado biome, located in a region yet poorly known. Methodology. We sampled 28 different areas representing seven habitat types found in the ENP. Small mammals were surveyed during rainy and dry seasons with live and pitfall traps. The total effort was 10,664 trap-nights for live and 2,898 trap-nights for pitfall traps. The data analysis consisted of rarefaction curves, estimates of species richness, data on relative abundance, diversity and evenness indexes, as well as the faunal composition in each habitat type and in ENP in order to observe how the assemblage is characterized and distributed in the landscape to better understand the biogeography of this southwestern region in the Cerrado. Results. We recorded 23 species of marsupials and small rodents in ENP. The grass mouse Necromys lasiurus was the most abundant, with the majority of species being rare. More species and individuals were encountered during the rainy season, with gallery forests and arboreal dense savannas representing the richest habitats. The assemblage was composed by two species groups: one inhabiting the forests and the other the open areas. Species composition overlaps with those of adjacent biomes and other Cerrado regions, but we found endemic and southwestern restricted species, characterizing an assemblage most similar to the Pantanal and Chaco biomes. Discussion and conclusions: Previous studies in the Cerrado have shown a higher richness and abundance during the dry season. Our results could be explained by the higher abundance (reproduction period) and activity (abundance of resources) during the rainy season. The habitat selectivity results showed the great importance of canopy and humidity on the distribution of small mammals, with gallery forest being not the richest habitat in the region. The high richness also found in the savannas, although less stratifi ed vertically, may be a result of horizontal heterogeneity. Other biomes adjoin the Cerrado and infl uence its faunal composition; compared to the Amazon and Atlantic Rainforest, the fauna of the present study showed greater similarity with the Amazon, contrary to prior studies. This pattern is mainly related to the presence of four taxa that occur in both the Amazon and Cerrado, but are replaced by sister groups in the Atlantic Rainforest. This study highlights the importance of this protected area, as it harbors a high richness of nonvolant small mammals, including endemic species and also species with restricted distributional ranges within the Cerrado, together with a unique faunal composition, characteristic of the southwestern portion of this biome.