The Mantadia-Zahamena corridor of Madagascar contains some of the country's last remaining low- and mid-elevation rainforests. This French-language volume presents the results of an expedition to survey the biodiversity of the region, during which three sites of high biological importance were identified based on species richness, abundance, and disturbance. Given the paramount significance of Madagascar in global conservation efforts and the high value of Mantadia-Zahamena in particular, the researchers conclude that these three sites deserve immediate conservation action. This report also documents the discovery of new species of frogs and reptiles and sixteen new species of ants.