The effect of male parallel dispersal on the kin composition of groups in white-faced capuchins

• Animals sometimes disperse together with familiar animals (i.e. parallel dispersal).
• We investigated how male parallel dispersal affects access to kin in capuchins.
• Parallel dispersing males were more closely related to one another than were other males.
• Parallel immigrants resided with a higher number of kin than did single immigrants.
• Parallel dispersal offers an opportunity for males to cooperate with familiar kin.

Sex-biased dispersal can reduce kin cooperation and kin competition in the dispersed sex. However, this may not be the case when group-living animals engage in parallel dispersal, which occurs when an individual transfers between groups together with other animals or immigrates alone into a group that contains familiar animals. Despite this potential effect on kin cooperation and competition, few studies have thoroughly investigated how parallel dispersal affects the kin composition of groups. To further our understanding of this topic, we investigated the effect of parallel dispersal on access to coresident kin in male white-faced capuchins, Cebus capucinus. Between 2006 and 2013, we collected demographic and genetic data from two to five groups in Sector Santa Rosa, Costa Rica. We genotyped 41 females and 39 males at 14 short tandem repeat loci, and we calculated their estimated relatedness values. The majority of males dispersed in parallel, and parallel dispersing males were more closely related to one another than were other males. Parallel immigrant males and natal females resided with a similar number of same-sex kin. Single immigrant males in multimale groups rarely resided with male kin, and they resided with fewer same-sex kin than did parallel immigrant males and natal females. Because parallel dispersal offers an opportunity for males to form long-lasting cooperative relationships with familiar kin, this dispersal pattern should be taken into account in future models of the evolution of social structure.