The goal of this project is to mitigate the invisible threat of hybridisation from invasive non-native marmoset species into native Buffy-headed marmoset through the implementation of population management campaigns to reduce the population of invasive non-native marmoset populations inside the protected areas and the National Park limits. Awareness campaigns to reduce the habit of releasing non-native marmosets in the private protected areas and in the forests surrounding the Caparaó town, and to reduce disease transmission from human to wild marmosets due to the habit of feeding the animals, will be conducted. Along with these activities, this project aims to evaluate the population status of the Buffy-headed marmoset after the last yellow-fever outbreak in Atlantic Forest, since recent studies have shown that the yellow fever epidemic appears to be largely responsible for a 90% population decline in at least one major sub-population (Possamai et al. 2019), and determine the current population and spatial distribution distribution of Callithrix flaviceps in the three protected areas is important to species conservation.