The Itaipu Binacional Hydroelectric plant owns 8 protected areas within the Upper Parana Atlantic Forest on the Paraná River located between Paraguay and Brazil. As part of the Mazama gouazoubira (brown brocket deer) and Pecari tajacu (collared peccary) population reinforcement program, individuals of these species born in captivity will be readapted to the wild in enclosures built for that purpose in the Tati Yupi Nature Reserve. These Readaptation Enclosures measure approximately 4.5 hectares. Sampling of trees and shrubs was carried out with 7 transects of 150 m. long by 4 m. wide. The species were identified, and the DBH (diameter at breast height) was measured. Also, the contribution that these will represent to the diet was analyzed according to published scientific studies for these two species of ungulates. Results show that the diversity of species and the physiognomy of the forest corresponds to high forest in regeneration due to the history of use of the area. More than 41 species were found with 10 types of fruits. Of the species found, 15 (43% of the trees measured) and 11 species (24%) were cited as part of the diet of P. tajacu and M. gouazoubira, respectively. These data show that the animals will be in contact with a natural source of food and in an enclosure with characteristics similar to the habitat where they will be released in afterwards. During the project, the diet and movement of the animals will be monitored to test their re-adaptation to nature.