Grooming and social cohesion in primates: a comment on Grueter et al.

Grueter et al. have recently claimed that grooming time in primates is best explained by terrestriality, which they take to be a proxy for hygiene demand. We suggest that their results arise from a confound between terrestriality and other aspects of sociality, combined with a number of conceptual and sampling problems.     

Synchrony and exertion during dance independently raise pain threshold and encourage social bonding

Group dancing is a ubiquitous human activity that involves exertive synchronized movement to music. It is hypothesized to play a role in social bonding, potentially via the release of endorphins, which are analgesic and reward-inducing, and have been implicated in primate social bonding. We used a 2 × 2 experimental design to examine effects of exertion and synchrony on bonding. Both demonstrated significant independent positive effects on pain threshold (a proxy for endorphin activation) and in-group bonding. This suggests that dance which involves both exertive and synchronized movement may be an effective group bonding activity.     

Contrasts in social structure among black-and-white colobus monkey groups

Three types of Colobus guereza groups may be distinguished on the bases of size and composition, namely small one-male groups, large, one-male groups and multi-male groups. The social structure of each type of group is described in terms of the distribution of non-agonistic interactions, the frequency and distribution of agonistic behaviour and the organization of the roles of vigilance, territorial defence and leadership. A number of differences are found between the group types which appear to be related to the differences in group size and composition. It is suggested that these group types represent stages in the life-cycle of colobus groups, and that such an interpretation may help to resolve some of the conflicting reports in the literature.