Efeitos das variáveis ambientais e disponibilidade de frutos na distribuição espacial de vertebrados terrestres na Amazônia Oriental, Brasil

Abstract

Terrestrial vertebrate frugivores constitute one of the major guilds in tropical forests. Previous studies show that meso-scale distribution of this group is only weakly explained by variables such as altitude and tree basal area in lowland Amazon forests. For the first time we test whether seasonally limiting resources (water and fallen fruit) affect the dry season distribution in 25 species of terrestrial vertebrates. To examine the effects of the spatial availability of fruit and water on terrestrial vertebrates we use a standardized, regularly spaced arrangement of camera-traps within 25km2 of lowland Amazon forest. Generalized linear models (GLMs) were then used to examine the influence of five variables (altitude, distance to large rivers, distance to nearest water, and presence vs absence of fruits and flowers) on the number of photos on five functional groups (all frugivores, small, medium, large and very large frugivores) and on seven of the most abundant frugivore species (Cuniculus paca, Dasyprocta leporina, Mazama americana, Mazama nemorivaga, Myoprocta acouchy, Pecari tajacu and Psophia crepitans). A total of 279 independent photos of 25 species were obtained from 900 camera-trap days. For most species and two functional groups, the variation in the number of photos per camera was only significantly but weakly explained by the GLMs (deviance explained ranging from 17.4 to 56.8%). Generally, we found that the presence of water availability was clearly more important than the presence of fallen fruit for the groups and species studied. Large-bodied frugivores, and two of the more abundant species (C. paca and P. crepitans) were recorded more frequently closer to water bodies; while none of the functional groups nor most abundant species showed significant relationship with presence of fallen fruit. One functional group and three of the seven most common frugivore species assessed in the GLMs showed significant results with species-specific responses to altitude. Our findings provide information to understand functional groups and species-specific responses to cope with periods of water and fruit scarcity in lowland Amazon forest, providing baseline data for management and conservation plans for tropical forests