The main objective of this study was to evaluate how the rest-activity rhythm of a group of 17 A. fusciceps rufiventris is influenced by such geophysical factors and the presence of human visitors since this group is in seminatural conditions. We recorded motor activity on five adult females and five males for an average of 115.2 days with Actiwatch AW4 and Actiwatch Minis accelerometers. Spider monkeys displayed a typical diurnal motor activity rhythm with only minor activity during nighttime. Sunset affected activity time directly, while sunrise had the opposite effect. Average daily activity pattern has four prominent peaks of activity and were influenced by geophysical variables such as sunset, sunrise and photoperiod as well as by temperature. Human visitor activities also affected this spider monkey group's activity pattern. In conclusion, the results of this study provide evidence on the behavior regulation of this species and could be used to optimize animal welfare in semi-natural conditions.