Dynamics and fitness benefits of male-male sociality in wild Guinea baboons (Papio papio)

Abstract

Males living in multi-male groups display a wide range of relationships with co-resident males, varying from high levels of competition, intolerance and avoidance to cooperation, affiliation and social bonds. Despite the wide diversity of male-male relationship dynamics, the existence of multi-male associations and male-male bonds is puzzling, as males compete over un-sharable fertilization. Multimale associations can emerge as a result of increased between-group competition, which would necessitate communal defense of females. In groups characterized by stable male co-residence, social bonds are thought to develop in scenarios of medium to low within-group contest potential, which would make it feasible for males to invest in coalitionary support aimed at rank ascension. Accordingly, multi-male alliances and coalitions between strongly bonded males are linked to lower takeover likelihoods and/or enhanced male reproductive success in several mammalian species. Female choice can also play a role, with increased reproductive success for males that invest in heterosexual bonds and provide services like protection from harassment and infanticide, assistance in rearing young, and support in conflicts. In this context, male-male ritualized behaviors are crucial behavioral mechanisms that balance the trade-offs imposed by male co-residence and help regulate male-male relationships. These ritualized exchanges are hypothesized to function as a tension buffering mechanism during competitive contexts and/or as honest signals used to test relationship quality, maintain social bonds, and promote cooperation. Several findings suggest that greeting function varies from species to species and that, in some cases, this can be influenced by the level of male tolerance and cooperation.In this thesis I investigate the dynamics and fitness benefits of male-male sociality in wild Guinea baboons by exploring the presence of strong male-male bonds along with their effect on male reproductive success and the function of ritualized greeting behavior between males. Guinea baboons live in nested multilevel societies, with several "units" forming a "party", which regularly aggregate into "gangs". Males engage in highly ritualized greetings with an intense repertoire involving potentially harmful behaviors like genital fondling, which may be crucial to regulating social dynamics in such large and fluid communities. The presence of male-male affiliation and cooperation, combined with the relatively high level of female leverage in intersexual relationships, make this species an intriguing model to assess how the advantages conferred by male-male sociality play out in a highly tolerant multilevel system. I examine whether number and strength of social bonds and number of associated secondary males are associated with higher average relatedness or enhanced reproductive success, using social behavior, genetic relatedness, and paternity of 24 adolescent and adult males. I group size, composition and spatiotemporal cohesiveness (i.e. social organiz...

Male–male social bonding, coalitionary support and reproductive success in wild Guinea baboons

“…Compared to macaques, however, rates of coalitionary support in Guinea baboons are low (0.001 h –1 ; Assamese macaques, Macaca assamensis : 0.11 h –1 [17]; Barbary macaques: 0.01–0.21 h –1 [57]), mirroring the low rate of aggression [24]. Given the lack of a clear dominance hierarchy between males [24] and the presence of frequent instances of coalitions targeting other coalitions [29], it is unlikely that coalitions serve in rank ascension. Why Guinea baboon males engage in possibly risky coalitions and what benefits strong bonds and cooperation may confer requires further investigation.…”

“…6 years old). At this age, they already establish close affiliations and display strong bonds and coalitionary support [24,29] with adult males. All details about male presence and age category changes, age category assessment and criteria for subject selection/exclusion can be found in the electronic supplementary material, appendix S1, tables S1 and S2, and figure S1.…”