Sex differences in cooperative coalitions: a mammalian perspective

Abstract

In group-living species, cooperative tactics can offset asymmetries in resource-holding potential between individuals and alter the outcome of intragroup conflicts. Differences in the kinds of competitive pressures that males and females face might influence the benefits they gain from forming intragroup coalitions. We predicted that there would be a female bias in intragroup coalitions because females (1) are more like to live with kin than males are, and (2) compete over resources that are more readily shared than resources males compete over. We tested this main prediction using information about coalition formation across mammalian species and phylogenetic comparative analyses. We found that for nearly all species in which intragroup coalitions occur, members of both sexes participate, making this the typical mammalian pattern. The presence and frequency of female or male coalitions were not strongly associated with key socio-ecological factors like resource defensibility, sexual dimorphism or philopatry. This suggests that once the ability to form intragroup coalitions emerges in one sex, it is likely to emerge in the other sex as well and that there is no strong phylogenetic legacy of sex differences in this form of cooperation. This article is part of the theme issue ‘Cooperation among women: evolutionary and cross-cultural perspectives’.

New perspectives on the evolution of women's cooperation

“…Further substantiating the argument that access to kin does not sufficiently explain variation in cooperation, Smith and colleagues ([ 111 ], in this issue) found no phylogenetic signal for sex differences in intragroup coalition formation across mammals. They also found no support for the prediction that in female philopatric species, females are more likely to exhibit intragroup coalitions than females in other species.…”

“…Competition and cooperation are closely linked social strategies. The behavioural ecology literature provides many examples of males and females in group-living species using cooperative tactics to offset individual differences in rank and power and alter the outcome of intragroup conflicts [ 89 , 111 , 116 , 117 ]. The connection between competition and cooperation also emerges in research on women.…”

Mechanisms of equality and inequality in mammalian societies

“…[106] post-conflict reconciliation [107]banded mongoose ( Mungos mungo) both or neither sex (varies by group) philopatric; mixed sexes; insectivore (food is not defendable)coalitions (R) [73]; escorted pups heaviest at maturity and increased reproductive success [108]supplemental food prenatally increased offspring lifespan and post-natally increased lifetime reproductive success [18] tolerance of food sharing among close relatives [109]; equitably allocate care among group-mates when kinship masked [110] dispersive conflict resolution via evictions from group [111]wild horse ( Equus caballus) neither philopatric; mixed sexes; herbivore (food is not defendable)coalitions (N) [54] low and mid-ranking males interrupt consorts by high-ranking males [112] post-conflict reconciliation [113]bottlenose dolphin ( Tursiops truncatus) both sexes philopatric; mixed sexes; piscivore (food is not defendable)coalitions (N) [54] post-conflict reconciliation [114]Indo-Pacific dolphin ( T. aduncus )both sexes philopatric; mixed sexes; piscivore (food is not defendable)coalitions (N) [73] low and mid-ranking males interrupt consorts by high-ranking males [115] post-conflict reconciliation [116]killer whale ( Orcinus orca )both sexes philopatric; mixed sexes; piscivore /carnivore (most food is not defendable)intergenerational transfer of ecological knowledge [117] increases survival of grandoffspring [118]p...…”

“… a Philopatry scored as females (F), males, (M), both (B) or neither (N) sex remaining at home into adulthood; social organization reflects the sex composition of adults in the group, where ‘mixed’ refers to multiple adult males and females in the group; trophic guild reflects the typical diet for a species and whether that food is defendable (yes = defendable; no = non-defendable), for complete set of references, see [54]. For brevity, whenever possible, we cited early review papers.…”

“…both philopatric; mixed sexes; omnivore (most food not defendable) coalitions (N,R) [73] tolerated co-feeding limited to kin at playbacks [74] post-conflict reconciliation [75] olive baboon (P. anubis) females philopatric; mixed sexes; omnivore (most food not defendable) coalitions (N) [54]; social skills in infants linked to maternal care [76]; maternal sociality predict infant growth and reproduction [77] mothers experiencing more adversity had increased glucocorticoid levels and reduced offspring survival [78] mutual feeding tolerance by males of males and females sexes of different ages [60] cultural shift from competitive to peaceful troop [79] post-conflict reconciliation [67,80] yellow baboon (P. cynocephalus) females philopatric; mixed sexes; omnivore (most food not defendable) coalitions (N, R, CH) [54];…”