Tourists interact with wild monkeys across the globe, and in some situations, tourists may be encouraged to feed, photograph, and touch the monkeys. Although tourism has the potential to bring in money towards conservation goals and provides an incentive for the protection of natural habitats, close proximity and interactions with tourists can also have significant psychological impacts on the Barbary macaques. Fecal samples and stress-indicating behaviours, such as belly scratching, indicate that the presence of tourists has a negative impact on the macaques. Human activities such as taking photographs cause the animals stress, possibly because the people come too close to the animals and make prolonged eye contact (a sign of aggression in many primates). Macaques that live in areas close to human contact have more parasites and lower overall health than those that live in wilder environments, at least in part due to the unhealthy diets they receive as a result of feeding from humans.