Comunidades de mamíferos de pequeno, médio e grande porte em fitofisionomias pampianas: diversidade e uso de habitat

Abstract

The study was conducted in an area of mixed grasslands of andropogoneae and composed and natural patches of Mesophytic Semideciduous Forest in the Central Depression of Rio Grande do Sul, Brazil. Between January 2011 and November 2012, the area was sampled monthly per four days/month using pitfall traps (five sets in the grasslands, and five sets in Forest) for small non-flying mammals. Additional methodologies of visual search (direct and traces) and one camera trap were employed to survey the mammals of medium and large size. We captured 28 individuals of small mammals, distributed in four species, all widely distributed and belonging to a single family Cricetidae. ANOSIM analysis, performed to the species of small mammals showed segregation between native forest and grassland. Axes were used in linear regression analyzes, which showed that both abundance and richness of small mammals in the warm season were negatively related to the first axis of the PCA. None of the predictors used was able to explain the richness and abundance of small mammals in the cold season. Environmental descriptors were collected in the warm and cold seasons, and summed up in axes of the Principal Component Analysis (PCA). The species accumulation curve (Collector curve) showed that new species records can still be made in the study area. Environmental descriptors who explained the abundance and diversity of small mammals in the warm season are related to forest environments (e.g., more shading, lower abundance and richness of invertebrates and larger diameter of trees). For mammals of medium and large size, have been recorded 16 native species and one exotic species (Lepus europaeus), belonging to 13 families. All recorded species are widely distributed geographically and the majority (eg Conepatus chinga, hydrochaeris) is considered tolerant to anthropogenic changes. Nevertheless, seven species recorded are considered endangered species: Alouatta caraya (Vulnerable), howler Alouatta (Vulnerable), cuniculus paca (Endangered), Dasypus hybridus (Near Threatened) Leopardus geoffroyi (Vulnerable), Otter longicaudis (Vulnerable) and Mazama gouazoubira (Vulnerable). Approximately 35% of the 17 species of medium and large registered were considered constant in the study area, 24% and 41% accessory were considered occasional. Most species were recorded in native forest (82%, 14 species), seven of which were unique to this vegetation type, were recorded in the field 59% of the species, only two in this phytophysiognomy. The predominance of records for mammals in the forest was expected due to the greater heterogeneity and resource availability in this environment, unlike the native grassland due to overgrazing which leads to homogeneity of the environment.