Melanophryniscus admirabilis is a splendid, Critically Endangered species, with a highly restricted distribution, endemic to one location (Perau de Janeiro, Arvorezinha), and with a great lack of information on its biology. Our study area in this project is located in the Perau de Janeiro, municipality of Arvorezinha, Rio Grande do Sul, Brazil, in the extreme south of the Atlantic Forest, one of the most diverse and endangered forest biome in the world. The species distribution is located in a region particularly vulnerable, since it is embedded in a river basin with great potential for the construction of hydroelectric power plants. In addition, the Perau de Janeiro is located in one of the last fragments of Atlantic Forest of the region, which have being destroyed mainly due to monoculture of eucalyptus and tobacco and cattle raising. The objectives of this project are to describe the reproductive behavior of Melanophryniscus admirabilis in order to understand how it is responding to environmental pressures, as the fluctuations in the river level. Additionally, this study aims to estimate genetic and demographic parameters, as well establish standard procedures for monitoring and managing this species in the future.