Abstract # 1838 Event # 108:

Scheduled for Friday, August 18, 2006 09:45 AM-10:00 AM: Session 10 (Regency East #2) Oral Presentation

Sex-biased inter- and intra-group social behavior in wild white-faced sakis (Pithecia pithecia), Brownsberg Nature Park, Suriname

C. L. Thompson1 and M. A. Norconk1,2
1Anthropology, Kent State University, Lowry Hall, Kent, OH 44240, USA, 2School of Biomedical Sciences, Kent State University
     Pronounced sexual dichromatism makes white-faced sakis an intriguing species to examine for evidence of sex-biased social behavior. We examined within-troop proximity and social interactions as well as participation in between-troop encounters in two groups of free-ranging white-faced sakis from May 30 to August 5, 2005 (204.5 observation hours). One group contained 1 adult male, 2 subadult males and 2 adult females and the other group contained 1 adult male, 1 adult female, 1 subadult female, and 1 juvenile. We found significant bias in within group spatial proximity for both troops (chi-square=11.4, p=0.003; U=351.0, p=0.001), although the sexes spending the most time together were reversed between the two groups. Asymmetry in social interactions occurred as well: females groomed males significantly more than expected while males groomed females and each other less than expected (chi-square=114.5, p<0.001). Additionally, females approached one another and males more often than expected; males approached other males less than expected (chi-square=12.9, p=0.002). Despite these differences, overall responsibility for proximity maintenance was equal between the sexes (Hinde Index=0.045). Active engagement in intergroup encounters was exclusively male. Females were generally somewhat distanced from the encounter zone, although they often gave vocalizations prior to and during encounters. These data suggest that in white-faced sakis responsibility for maintaining intra-group contact among group members is shared between males and females, but investment in territorial behavior is biased toward males.