London: Feeding wild monkeys can pose a risk to their health as it makes them larger in size, more susceptible to disease, and more stressed, warns new research. The study was conducted on Barbary macaques, an endangered species of apes found majorly in the European continent. The findings showed that the macaques that ate food from tourists were found to have poorer quality of fur, alopecia -- patchy hair loss -- and also suffered from higher levels of stress hormones compared with the other group. Also, only a third of female macaques, fed by tourists could conceive, while all the females in the non-fed group gave birth. While the monkeys which relied on natural food suffered from only one incident of a stomach upset, the group that received large amounts of food from tourists had 32 bouts of illness. In addition, the females fed by tourists had larger body sizes, but had better coat quality. Tthe males, however, suffered more from patchy loss of hair as well as had higher levels of stress. "Our findings support previous research, which indicates that wildlife tourism, and particularly so-called 'tourist provisioning', has negative impacts on the health of wild animals," said Laetitia Marechal, post-doctoral fellow at University of Lincoln in Britain. For the study, detailed in the journal PLOS ONE, the team compared the health of two groups of wild Barbary macaques in Ifrane National Park in the Atlas Mountains, Morocco. They assessed the primates' health using a range of non-invasive measures, such as birth and survival rates, the quality of their fur, body size, occurrence of injury and disease, and stress hormone levels in fecal samples. Measures need to be taken to avoid causing more harm to an already endangered species, the researchers suggested.