Multilevel Organisation of Animal Sociality

Abstract

Multilevel societies (MLSs)-stable nuclear social units within a larger collective encompassing multiple nested social levels-occur in several mammalian lineages. Their architectural complexity and size impose specific demands on their members requiring adaptive solutions in multiple domains. The functional significance of MLSs lies in their members being equipped to reap the benefits of multiple group sizes. Here we propose a unifying terminology and operational definition of MLS. To identify new avenues for integrative research, we synthesise current literature on the selective pressures underlying the evolution of MLSs and their implications for cognition, intersexual conflict, and sexual selection. Mapping the drivers and consequences of MLS provides a reference point for the social evolution of many taxa including our own species.

Group size and composition influence collective movement in a highly social terrestrial bird

“…Vulturine guineafowl live in a multilevel society, where groups preferentially associate with other groups ( Papageorgiou et al, 2019 ). In such societies, intergroup associations can bring many important benefits, such as information sharing on predators and resources, as well as mating and dispersal opportunities ( Grueter et al, 2020 ). A large home range size in a multilevel society could provide groups with access to more communal roosts (we have observed up to five groups in a single roost, Papageorgiou et al, 2019 ) and more glades, and thus more opportunities to associate with more groups.…”

“…In such species, groups can interact affiliatively and preferentially with specific other groups, resulting in a multilevel society. In such societies, having a larger home-range size might generate more chances to associate with conspecifics from other groups ( Grueter et al, 2020 ), which, in turn, can increase mating opportunities (by increasing contact with members of the opposite sex; Grueter et al, 2015 ), dispersal opportunities (as sub-adults often disperse to neighbouring groups; Städele et al, 2015 ) and information sharing about food resources or predation risk ( Whitehead et al, 2012 ). Thus, there are many ways that groups can benefit from maximizing their space use, up to the point where the costs of travel and navigation do not override the benefits gained.…”

Versatile counterstrategies shift the balance of intersexual conflict from males to females

“…Some females have sexual experienced with other resident male int the band, this might also offer her and her unweaned infant a refuge when there is high risk of infanticide. In addition, food competition among the band member in this species is low because ubiquitous lichens and leaves form a major dietary constituent throughout the year (Li 2006), facilitating units to be in close proximity to potentially reduce predatory attacks through travelling, feeding, and resting within the same areas (Grueter et al 2020).…”

“…Based on the insight that the trade-off between current and future reproduction, animal personalities could be given an adaptive explain in polymorphic population (Wolf et al 2007). In snub-nosed golden monkeys of a multilevel society, where multiple OMUs coordinate and forage together as one larger social band (Grueter et al 2020), social complexity would allow polymorphic personality of resident male in the band. In this study, we have observed two kinds of male personalities towards unweaned infants following male replacement.…”

“…Golden snub-nosed monkeys (Rhinopithecus roxellana ) are Asian colobines endemic to China living in a multi-level society, in which females reside in core social units consisting primarily of one male unit (OMU) with multiple females, and multiple such OMUs associate and forage together as one larger social band (Xiang et al 2014;Grueter et al 2020). Infanticide has been observed when males take over the dominant position in OMUs (Yao et al 2016), but most unweaned infants present during the times of male replacement survive without being attacked by the new male.…”