Spatial position selection during collective movement in a nonhuman primate species with a multilevel social structure (Rhinopithecus roxellana)

Abstract

AbstractSubstantial phylogenetic differences in the evolution of decision-making in group-living animals are observed in the animal kingdom. Decision-making is vital for maintaining a cohesive social structure, health, survival, and reproductive fitness. Thus, exploring such mechanisms in diverse social species living in the wild, especially nonhuman primates, provides insight into the coordinating rules, behaviors, regulations, and laws in human society. The golden snub-nosed monkey (Rhinopithecus roxellana) is characterized by a multilevel social system. The present study investigated individual spatial positioning during collective movements at departure and determination of consensus during decision-making. The results indicate that individuals traveling in the front of the group determine whether a collective movement succeeds or fails. These front positions provide various benefits and are typically occupied by adults in one-male units (OMUs). In addition to the hypotheses of protection and food resource competition proposed for species with a single-level social system, we suggest that communication between and within OMUs also plays an essential role in achieving consensus decisions. Social affiliations among individuals also significantly influence decision-making via mediation effects, a phenomenon observed in sophisticated multilevel societies. Thus, these findings illuminate avenues for further research on how communications between and within groups contribute to consensus decisions and how such decisions are initiated at lower levels and developed at higher levels in a multilevel society. Such avenues can provide insight for primatologists and social anthropologists.