“Friendships” between new mothers and adult males: adaptive benefits and determinants in wild baboons (Papio cynocephalus)

Abstract

Close associations between adult males and lactating females and their dependent infants are not commonly described in non-monogamous mammals. However, such associations [sometimes called “friendships” (Smuts 1985)] are regularly observed in several primate species in which females mate with multiple males during the fertile period. The absence of mating exclusivity among “friends” suggests that males should invest little in infant care, raising questions about the adaptive significance of friendship bonds. Using data from genetic paternity analyses, patterns of behavior, and long-term demographic and reproductive records, we evaluated the extent to which friendships in four multi-male, multi-female yellow baboon (Papio cynocephalus) groups in Amboseli, Kenya represent joint parental care of offspring or male mating effort. We found evidence that mothers and infants benefited directly from friendships; friendships provided mother–infant dyads protection from harassment from other adult and immature females. In addition, nearly half of all male friends were the genetic fathers of offspring and had been observed mating with mothers during the days of most likely conception for those offspring. In contrast, nearly all friends who were not fathers were also not observed to consort with the mother during the days of most likely conception, suggesting that friendships between mothers and non-fathers did not result from paternity confusion. Finally, we found no evidence that prior friendship increased a male’s chances of mating with a female in future reproductive cycles. Our results suggest that, for many male–female pairs at Amboseli, friendships represented a form of biparental care of offspring. Males in the remaining friendship dyads may be trading protection of infants in exchange for some resources or services not yet identified. Our study is the first to find evidence that female primates gain social benefits from their early associations with adult males.

Social affiliation matters: both same-sex and opposite-sex relationships predict survival in wild female baboons

“…Here, we found that higher female social connectedness to males was predicted by higher female dominance rank. This result suggests that male baboons are a limited, monopolizable resource for females, and females who effectively compete for access to males may experience higher survival, as well as reproductive benefits [38,41,50]. However, in our data, we did not observe a direct effect of female rank on survival.…”

“…Second, many primate species exhibit close social relationships among adult males and females (sometimes called 'friendships') [27][28][29][30][31][32][33][34][35][36][37]. While the primary benefits of such friendships are thought to be reproductive, including bi-parental offspring care and access to potential mates [28,36,[38][39][40][41][42][43][44][45][46][47][48][49], heterosexual friendships may also benefit females directly via reduced harassment, reduced predation risk or stress mitigation [38,39,[50][51][52].…”

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

“…Taub 1980). In some baboon species, these preferences may reflect likelihood of paternity to some extent (Nguyen et al 2009;Moscovice et al 2010). In macaques male preferences for infants appear mostly unrelated either to paternity or to past mating (Paul et al 1992;Ménard et al 2001; but see Ménard et al 1992 andOstner et al 2013) but may reflect the male's social relationships with the mother and may be predictive of future mating opportunities (Ménard et al 2001; see also Smuts and Gubernick 2015).…”

Male-Driven Grooming Bouts in Mixed-Sex Dyads of Kinda Baboons (Papio kindae)

“…For instance, grooming has been interpreted as a tactic used, usually but not exclusively by females, to gain access to an infant Smuts [1985] (olive), Swedell [2006] (hamadryas), Nguyen et al [2009] (yellow), Huchard et al [2010] (chacma) and this study (Kinda). [Nicolson, 1987;Henzi and Barrett, 2002].…”