About 90% of the Amazon’s energy potential remains unexploited, with many large hydroelectric dams yet to be built, so it is important to understand how terrestrial vertebrates are affected by reservoir formation and habitat loss. We investigated the influence of the construction of the Santo Antônio Hydroelectric dam on the Madeira River in southwestern Amazonia on the structure of frog assemblages based on samples collected in two years before the dam flooded (pre-stage) and one (post1-stage) and four years (post2-stage) after its construction. We surveyed five 500-ha plot systems three times during each stage; in the pre-stage we sampled 19 plots in low-lying areas that would be flooded by the dam, (from now called flooded pre-stage plots) and 45 plots in terra-firme forest (from now called unflooded pre-stage plots). At the post1-stage we sampled the 45 unflooded plots and in the post2-stage we sampled the remaining 39 unflooded plots. We detected frogs by active visual and acoustic searches standardized by both time and sampling area. Few species recorded in the pre-stage flooded plots were not found in the pre-stage unflooded plots or in stages after flooding. However, the composition of frog assemblages based on relative densities in flooded pre-stage plots did not re-establish in plots on the new river margins. In unflooded areas, frog assemblages were distinct among the flooding stages with no tendency to return to the original assemblage compositions even four years after the dam was filled. For the areas that were not flooded, there was an increase in species richness in 82% of the plots between the surveys before dam construction and the first surveys after dam completion, and 65% between the pre-stage and surveys four years after dam completion. Lack of understanding by the controlling authorities of the long-term effects of landscape changes, such as water-table rises, means that studies covering appropriate periods post construction are not required in legislation, but the data from Santo Antônio indicate that changes due to dam construction are either long-term or difficult to distinguish from natural fluctuations. Future environmental-impact studies should follow strict BACI designs.

This article provides a new record for Typhlops amoipira from municipality of Bonito de Minas, state of Minas Gerais. The record extends its distribution about 500 km southern from the type locality at Ibiraba, state of Bahia. The collection site is also located on the left bank of the São Francisco River, and is dominated by cerrado sensu stricto with sandy soils, Veredas and riparian forests, in a transitional region between Cerrado and Caatinga biomes. This record confirms that the occurrence of T. amoipira goes beyond the borders of the Caatinga biome.

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We provide records for Micrablepharus maximiliani from state of Minas Gerais and present a map representing its distribution. The record of M. maximiliani from municipality of Resplendor, Minas Gerais, represents a distribution extension of 1,050 km southern from the type locality at the municipality of Maruim, Sergipe. Others 57 new records are presented based on specimens housed in several Brazilian and Paraguayan herpetological collections, improving the knowledge on geographic distribution of M. maximiliani in South America.

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