The main objectives of this study are the evaluation and quantification of the inorganic and organic mercury (methylmercury) levels in water, fish and fish-eating predators tissues, especially in the Giant Otter (Pteronura brasiliensis), of distinct areas of the Tambopata National Reserve (TNR) in the region Madre de Dios (Mother of God) region - Peru, which presents high levels of mercury contamination as a consequence of small-scale gold mining activities. An evaluation of how the South Interoceanic Highway, built only 25 km away from the legal limits of the TNR, could influence the increment of mining activities in the surroundings of the study area, and further threatening the living conditions of the aforementioned species, will also be performed. The techniques proposed for the chemical analysis of the sample are cold vapor atomic absorption spectrometry (CVAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES), for total mercury determination; and inductively coupled plasma mass spectrometry (ICP-MS) and gas chromatography with electron capture detection (GC-ECD), for organic mercury determination (methylmercury).