Abstract # 2780 Event # 135:

Scheduled for Saturday, June 19, 2010 01:30 PM-01:40 PM: Session 25 (Medallion Ballroom B) Oral Presentation


C. Guillier and B. Chapais
Université de Montréal, Département d'Anthropologie, C. P. 6128, Succursale Centre-Ville, Montréal, Québec H3C 3J7, Canada

The existence of preferential relationships between same-sex kin is well documented in Old World primates. In contrast, little is known about intersexual nepotism, including nepotism between brothers and sisters. The aim of this project is to describe relationships between immature brothers and sisters in a group of olive baboons (Papio anubis) housed at the Station de primatologie du CNRS in Rousset-sur-Arc (France). We compared the affiliative interactions of 11 brother-sister dyads (in which males were consistently younger than their sisters) with those of unrelated males and females of similar age and dominance rank. Sisters showed a preference for their brother as measured by rates of contact and play [Wilcoxon test: contact: n=11, z=-2.310, P=0.021; play: n=11, z=-111.992, P=0.046], whereas brothers showed a preference for their sister as measured by rates of proximity and contact [proximity: n=11, z=-2.803, P=0.005; contact: n=11, z=-2.402, P=0.016]. However, brothers did not prefer their sister as a play partner [n=11, z=-1.153, P=0.249]; they preferred to play with same-sex peers [same sex: n=8, z=-2.521, P=0.012; same age: n=8, z=-2.521, P=0.012]. The most important variable affecting brother-sister relationships was their age difference, which was negatively correlated with all affiliative indices [Pearson Correlation: proximity: n=11, r=-0.684, P=0.020; contact: n=11, r=-0.731, P=0.011; play: n=11, r=-0.609, P=0.047]. These results suggest the existence of intersexual nepotism among immature baboons.