Social Bonds Enhance Reproductive Success in Male Macaques

Abstract

For animals living in mixed-sex social groups, females who form strong social bonds with other females live longer and have higher offspring survival [1-3]. These bonds are highly nepotistic, but sometimes strong bonds may also occur between unrelated females if kin are rare [2, 3] and even among postdispersal unrelated females in chimpanzees and horses [4, 5]. Because of fundamental differences between the resources that limit reproductive success in females (food and safety) and males (fertilizations), it has been predicted that bonding among males should be rare and found only for kin and among philopatric males [6] like chimpanzees [7-9]. We studied social bonds among dispersing male Assamese macaques (Macaca assamensis) to see whether males in multimale groups form differentiated social bonds and whether and how males derive fitness benefits from close bonds. We found that strong bonds were linked to coalition formation, which in turn predicted future social dominance, which influenced paternity success. The strength of males' social bonds was directly linked to the number of offspring they sired. Our results show that differentiated social relationships exert an important influence on the breeding success of both sexes that transcends contrasts in relatedness.

Postdispersal nepotism in male long‐tailed macaques (Macaca fascicularis)

“…Schuelke et al. 2010). In this study, we therefore examined two correlates of fitness, residence time and high‐rank tenure, in this species.…”

Coalitions in theory and reality: a review of pertinent variables and processes

“…Coalitions can occur opportunistically on a case-by-case basis (e.g., Bissonnette, 2009;Smith et al, 2010), or they can be observed frequently among the same partners as part of an enduring, long-term relationship (e.g., de Waal, 1982;Packer & Pusey, 1982;Smuts, 1985;Goodall, 1986;Noë, 1986b;Caro & Collins, 1987;Connor et al, 1992Connor et al, , 2001Feh, 1999;Boesch & BoeschAchermann, 2000;Boinski et al, 2005;Schülke et al, 2010). One individual may establish year-long, stable alliances with one or a few partners and also participate in opportunistic coalitions with other group members in which loyalties change regularly (Riss & Goodall, 1977;de Waal, 1982;Goodall, 1986;Noë, 1990;Uehara et al, 1994;Connor et al, 2000;Sijtsema et al, 2010).…”

“…As we will see below, coalitions can serve different functions (van Schaik et al, 2006); they can be observed among different sex and age classes (reviewed in Chapais, 1995); they can involve kin (e.g., Riss & Goodall, 1977;Chagnon & Bugos, 1979;Wahaj et al, 2004), non-kin (e.g., Vigilant et al, 2001;Langergraber et al, 2007;Schülke et al, 2010), and friends or acquaintances (Hruschka & Henrich, 2006;Hruschka, 2010). As this brief review makes clear, coalitionary patterns are varied, and understanding this diversity would be greatly enhanced by formal modelling that would allow us to identify the general conditions under which coalition formation is expected to evolve, characterize the degree of variability expected, and predict when coalitions should, and should not, occur.…”

“…In terms of investment cost, one can think of all behavioural or physiological expenditures that facilitate the formation of coalitions. For example, research on primates and other mammals indicates that some individuals may establish enduring relationships with other conspecifics (so-called 'friends', Smuts, 1985;Seyfarth & Cheney, 2012) with whom they often form coalitions (e.g., Smuts, 1985;Silk, 1994;Mitani et al, 2002;Langergraber et al, 2007;Schülke et al, 2010). The establishment of such relationships may take considerable time, even though all participants may eventually obtain a positive pay-off for their investment.…”

Triadic awareness predicts partner choice in male–infant–male interactions in Barbary macaques

“…This capacity helps the individual to avoid aggression (e.g. De Waal 1986;van Hooff and van Schaik 1994), to increase fitness (Silk et al 2003;Silk 2007a, b;Silk et al 2009;Schülke et al 2010) and contributes to the stability and cohesion of the group (e.g. Sterck et al 1997;Lehmann et al 2007).…”