The dataset contains records of the Otter (Lutra lutra) collected in the lower valley of River Sabor (NE Portugal), in the scope of the long-term Ecological Monitoring Program (PME) of the Baixo Sabor Hydroelectric Dams (AHBS), promoted by EDP – Energias de Portugal, S.A. This dataset includes results of surveys made in and around the area affected by the dam, from November 2010 to December 2014. Sampling was performed in transects distributed along the lower Sabor river valley (and some tributaries), and along the rivers Maçãs and Angueira, up to 42 km upstream. The presence and identity of the target species were assessed through the presence of faeces (spraints) and/or footprints of the target species.