Figure 3.

(a) Mean frequency of multi-partner grooming sets in individual groups of three catarrhine primates. Multi-partner grooming includes mutual grooming (figure 2, left photo), grooming chains (figure 2, right photo) and more complex forms. The large symbol in the bottom right corner indicates that two datapoints are superimposed. All data are from wild populations. The chimpanzee data represent both common chimpanzee and bonobo. The data are given in the electronic supplementary material, table S2. (b) Mean frequency of multi-party grooming for each species in (a), plotted against mean social group size (group for colobus, community for chimpanzees and band for gelada, respectively). Group size data from the electronic supplementary material, table S1.