Richness, abundance, and mass in snake assemblages from two Atlantic Rainforest sites (Ilha do Cardoso, São Paulo) with differences in environmental productivity

Abstract

We analyzed richness, composition and mass of snakes in two sites in the Atlantic forest of Ilha do Cardoso (25º 03' S and 47º 53' W), an island (22,500 ha), Cananéia municipality, São Paulo State, Brazil. A monthly index of arthropod availability (in mm³) was estimated in each site through capture rates in pit-fall traps. Fallen fruits were collected along trails in the study sites (mass of fruit gave an index of fruit availability) and small mammals were sampled in grids with 120 traps which covered the lowland (5.2 ha) and in the slope forests (3.6ha). The abundance and mass of small mammals were standardized for the size of each sampled area (in g.ha-1). To sample snakes we established 20 pit-fall traps in each area and performed monthly transects in four consecutive days (totaling 1000 m long) along trails in the study sites. Snakes found were measured, weighted marked and released. Abundance and total mass of snakes were standardized by the size of each area. The areas differed consistently in in the productivity of arthropods, fruits and small mammals, and also in richness, composition and total mass of snakes. We found 36 individuals (total mass = 9884 g) of 12 snake species belonging to three Families (Colubridae, Elapidae and Viperidae) in the lowland forest, whereas in the slope forest we sampled only 9 individuals of 2 species (total mass = 1820 g). Our results suggest that the area of lowland forest, showing higher productivity of arthropods, fruits and small mammals, maintains a snake community with a higher richness, diversity and biomass than its slope forest counterpart.