“…Although habituation is a complex and partially subjective process (Allan et al, 2020;Ampumuza & Driessen, 2020;Green & Gabriel, 2020), some observational measures may allow an objective assessment of this process. For each encounter, we therefore noted the following information: 1) habituation day and number of the encounter (for each group, two sequential numbers starting from 1); 2) group ID (i.e., Scuba or Merah); 3) shift (i.e., morning or afternoon); 4) number of researchers (range: 1-3); 5) exact duration of the encounter (in minutes); 6) minimum distance between the researchers and the closest macaque reached during the encounter (in meters); 7) position of the macaques when the encounter started (i.e., whether the majority of visible macaques were on the ground or on trees/high rocks higher than 2 m); and 8) area of the encounter (i.e., where the group was met), categorized as forest area (i.e., tropical secondary forest mixed with patches of pines and acacias for the Merah group and savannah forest with volcanic stones covered by shrubs for the Scuba group), field area (i.e., with crops), beach area (i.e., the shore, excluding resort and hotel facilities), path area (including primary and secondary roads, ground paths, and any open area with a minimum of 1-m width), or human area (i.e., including any other human buildings).…”