The limited impact of kinship on cooperation in wild chimpanzees

Abstract

The complex cooperative behavior exhibited by wild chimpanzees generates considerable theoretical and empirical interest, yet we know very little about the mechanisms responsible for its evolution. Here, we investigate the influence of kinship on the cooperative behavior of male chimpanzees living in an unusually large community at Ngogo in Kibale National Park, Uganda. Using long-term field observations and molecular genetic techniques to identify kin relations between individuals, we show that male chimpanzees clearly prefer to affiliate and cooperate with their maternal brothers in several behavioral contexts. Despite these results, additional analyses reveal that the impact of kinship is limited; paternal brothers do not selectively affiliate and cooperate, probably because they cannot be reliably recognized, and the majority of highly affiliative and cooperative dyads are actually unrelated or distantly related. These findings add to a growing body of research that indicates that animals cooperate with each other to obtain both direct and indirect fitness benefits and that complex cooperation can occur between kin and nonkin alike.Pan troglodytes ͉ genotyping ͉ kin recognition ͉ microsatellites ͉ relatedness

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

“…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.…”

“…A strong bias towards female philopatry (Smuts, 1987), however, limits the occurrence of male-male nepotistic coalitions in primates. As a result, increasing one's inclusive fitness is not expected to be a major benefit of coalitions among primate males (Chapais, 1995;van Schaik et al, 2006), with rare exceptions (Langergraber et al, 2007).…”

“…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.…”

“…In a coalitionary context it often makes sense to choose the strongest partner at hand, and indeed several studies suggest that primates choose coalition partners based on their competitive value (i.e., ability to help, usually equivalent to dominance or RHP, Chapais, 2006;e.g., Noë, 1994;Noë & Sluijter, 1995;Mitani et al, 2002;Langergraber et al, 2007;Bissonnette et al, 2009a;Higham & Maestripieri, 2010). Silk (1999), for example, showed that male bonnet macaques chose allies that outranked themselves and their opponents more often than expected by chance.…”

“…Observations of female white-faced capuchins, gorillas and white-nosed coatis also reveal that, like female Old World monkeys, individuals are more likely to aid their kin instead of non-kin in disputes (Watts, 1997;. In studies of white-faced capuchins, Barbary macaques, bonnet macaques, chimpanzees and bottlenose dolphins, males sometimes form coalitions with their kin more often than with non-kin (Silk, 1992;Widdig et al, 2000;Langergraber et al, 2007; but see Vigilant et al, 2001). In some species mothers are known to provide aid to sons in conflicts with other males (Surbeck et al, 2011; see also Chapais, 1983;Kutsukake & Hasegawa, 2005).…”