New Route of Investigation for Understanding the Impact of Human Activities on the Physiology of Non-Human Primates

Abstract

The present study is aimed to assess the impact of human presence on the physiology of the folivorous Goldenmantled Howler Monkey (Alouatta palliata palliata) and the frugivorous Ornate Spider Monkey (Ateles geoffroyi ornatus) in Tortuguero conservation area in North-eastern Costa Rica. We compared fecal cortisol and fecal testosterone levels between non-habituated monkeys sighted in an area with high human presence (HHP) and in an area with low human presence (LHP). Both sexes of howler monkeys, but not spider monkeys, secreted significantly more cortisol when encountered in the area with HHP. Also, males, but not females, of both species showed higher levels of fecal testosterone when encountered in the area with HHP. In the area with HHP, we found that the proximity to human settlements was the type of human presence inducing the largest rise of cortisol secretion in howler monkeys. On the contrary, the proximity to the canal - which was intensively frequented by motor boats (i.e: ≥80 boats per day) linked to tourism activities – was the type of human presence inducing the largest rise of testosterone secretion in males of both species sighted in area with HHP. Our results suggest that human presence impacts levels of fecal cortisol and fecal testosterone in non-human primates (NHPs), but these impacts could differ across sexes and species. This study opens new investigation perspectives aiming to increase our understanding of the relationship between NHPs’ physiology, biology and ecology, as well as mitigating perturbation of human activities on wildlife.