RESEARCH ARTICLE Mixed-Species Associations in Cuxi (Genus Chiropotes)

Polyspecificormixed-speciesassociations,wheretwoormorespeciescometogethertoforageandtravelas a unit, have been reported in many primate species. These associations appear to offer a number ofbenefits to the species involved including increased foraging efficiency and decreased risk of predation.While several researchers have suggested that cuxius (genus Chiropotes) form mixed-speciesassociations, previous studies have not identified the circumstances under which cuxius formassociations or whether they form associations more often than would be expected by chance. Here wepresent data on the formation of mixed-species associations by four species of cuxius at eight differentsites in Brazil, Suriname, and Guyana. We analyzed data from two of the study sites, (BiologicalDynamics of Forest Fragments Project (BDFFP), Brazil and the Upper Essequibo ConservationConcession (UECC), Guyana, to assess whether associations occurred more than would be expected bychance encounters and identify the factors influencing their formation. Cuxius showeda high degree ofinter-site variation in the frequency of time spent in association (ranging from 2 to 26% of observationtime) and duration of associations (mean duration from 22min to 2.5hr). Sapajus apella was the mostcommon association partner at most sites. At BDFFP, cuxius formed associations more frequently butnot for longer duration than expected by chance. For much of the year at UECC, associations were notmore frequent or longer than chance. However, during the dry season, cuxius formed associations withS. apella significantly more often and for longer duration than predicted by chance. Cuxius at UECCformed associations significantly more often when in smaller subgroups and when foraging for insects,and alarm called significantly less frequently during associations. We suggest cuxius form mixed-species associations at some sites as an adaptive strategy to decrease predation risk and/or increaseforaging efficiency. Am. J. Primatol. © 2015 Wiley Periodicals, Inc.Key words: polyspecific association; bearded sakis; Guyana; Brazil; SurinameINTRODUCTIONPolyspecific or mixed-species associations in-volve two or more species coming together to forageand travel as a unit [Cords, 1990a]. These associa-tions occurinadiverserange oftaxa,including birds[Munn & Terborgh, 1979; Powell, 1985], ungulates[Sinclair,1985],andfish[Wolf,1985],aswellasNewWorld monkeys [Hardie & Buchanan-Smith, 1997;Norconk, 1990; Porter, 2001; Rehg, 2006; Terborgh,1983], Old World monkeys [Chapman & Chapman,2000; Cords, 1990a; N€oe & Bshary, 1997; Oates WWolters&Zuberbuhler,2003],and€lemurs [Sauther, 2002], leading researchers to