Unravelling the function of community-level organization

Abstract

First paragraph: Multi-level and fission-fusion social systems are relatively uncommon across the animal kingdom: most group-living species live in at least temporarily stable social groups, where all members of the group form a relatively cohesive group. However, there are two major deviations from this scheme. In some species, small cohesive (usually reproductive) units, such as families or one-male units with attached females and offspring, aggregate regularly with other small cohesive units, thereby forming higher level groupings. This type of multi-layered sociality has e.g. been shown for African and Asian elephants (Moss &Poole 1983, Wittemyer et al. 2005; de Silva et al., 2011), zebras (Rubenstein & Hack 2004), whales (Baird 2000, Whitehead et al. 1991), prairie dogs (Hoogland 1995), horses (Linklater 2000), parrots (Wanker et al., 1998) and several primate taxa, including the African papionins Papio hamadryas and Theropithecus and some Asian colobines (notably Rhinopithecus, Nasalis and Pygathrix). In all these cases, the small unit is the stable social unit with higher level groupings being built out of these smaller units; multi-level sociality is thus achieved via a bottom-up mechanism with small stable groups flexibly aggregating into larger, more fluid groupings (of which several layers can exist).