Behavior patterns of Southern Bearded Sakis ( Chiropotes satanas ) in the fragmented landscape of Eastern Brazilian Amazonia

The endangered but poorly studied southern bearded saki, Chiropotes satanas, faces extremes of habitat fragmentation throughout its geographic range in eastern Amazonia. This article focuses on the behavior of the members of two groups—a large one (30–34 members) in continuous forest (home range=69 ha) and a much smaller one (7 members) on a 17‐ha man‐made island—at the Tucuruí Reservoir on the Tocantins River. Quantitative behavioral data were collected through scan and all‐events sampling. Both groups were characterized by the fission–fusion pattern of social organization typical of the genus and relatively high rates of traveling and feeding, also characteristic of the genus. However, the island group spent significantly more time resting and significantly less traveling than the mainland group, presumably as a function of its much smaller home range. Despite resting more, island group members engaged in significantly less social interaction, possibly because of the much smaller size of this group (which also affected visibility), or other factors, such as nutritional stress. Affiliative associations of males were a mainstay of social behavior in both groups and interspecific associations with capuchins ( Cebus apella ) and squirrel monkeys ( Saimiri sciureus ) were relatively common, especially in the mainland group. Overall, the island group presented a relatively reduced behavioral repertoire, apparently reflecting factors such as group size and the size and quality of its home range. Am. J. Primatol. 71:1–7, 2009. © 2008 Wiley‐Liss, Inc.