Different types of temperament and personality can affect various ecologically relevant aspects, such as the way in which animals respond to environmental disturbances, potentially influencing animal health and survival. The golden-headed lion tamarin is a primate endemic to the Atlantic Forest of southern Bahia, and threatened with extinction. Understanding how the personality of these animals can influence health and social aspects influencing their survival and reproduction, can be of great importance for the conservation of the species. Thus, individuals belonging to four groups of GHLTs ranging in areas under different pressure from human activities (degraded fragments and shade cocoa plantation) will be studied to evaluate the relationship between personality, social relationships and parasite load. Behavioral and physiological data will be collected individually over two years. We will investigate the role of personality in two natural situations: 1) territorial encounters between different groups, and 2) use of matrix and open areas between  forest fragments. We will investigate the relation between personality and parasite load, predicting that bolder animals will have a higher parasite load. In addition, we will investigate the existence of polymorphisms in genes of the neuropeptides oxytocin receptors and
vasopressin and the relationship with the sociality of animals.