Revolutionary coalitions in male rhesus macaques

Coalitions between animals are found in a variety of taxa, but are most common among primates. Here, we present data on the relative abundance of male-male coalitions within a group of free-ranging rhesus macaques, a species in which male coalitions are reportedly rare or absent. We then report a series of revolutionary coalitions among subordinates against higher ranked individuals that transformed male dominance relationships. We use these data to test theoretical model predictions about revolutionary rank-changing coalitions among primate males. We also use data on male age, rank, group residency length, associations and relative fighting ability (morphometric variables), to test predictions about coalition members' characteristics. Contrary to model predictions, coalition sizes were large, but consistent with predictions, targets were high ranking, and members middle ranking. Coalition males were more similar to each other in rank, group residency length and body mass than other males were. Coalition members were also associates (spent more time with other members than non-members did in the preceding months), and had longer canines than other males. Our results show that males forming revolutionary coalitions were from a specific part of the male distribution and represent the first systematic analysis of male-male coalitions in free-ranging rhesus macaques.