Sexual conflict in a polygynous primate: costs and benefits of a male-imposed mating system

Swedell, Larissa; Leedom, Liane J.; Saunders, Julian; Pines, Mathew

doi:10.1007/s00265-013-1641-3

Cited by 44 publications

(58 citation statements)

References 73 publications

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“…The results of our analyses confirm previous findings concerning the impact of raising infants to weaning age on the mother’s length of the IBI [22], [51], [52], and lend further support to the view that male infanticide is clearly reproductively advantageous to males as it eliminates the barrier that delays the mothers’ resumption of ovarian activity [30]. More importantly, our findings reveal that male takeovers are reproductively costly to females, because females abducted during takeovers take longer to conceive and therefore have significantly lengthened IBIs.…”

Section: Discussionsupporting

confidence: 90%

Male Takeovers Are Reproductively Costly to Females in Hamadryas Baboons: A Test of the Sexual Coercion Hypothesis

2014

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During male takeovers, in addition to fighting off the female’s current mating partner, males may exhibit intense aggressive mate guarding of the newly acquired females. Recent studies indicate that coercive sexual aggression by males is an important strategy through which sexual conflict is expressed. Previous tests of the sexual coercion hypothesis in primates have focused on assessing if female mate choice is effectively reduced by male aggression, however, only one recent study has tested a critical prediction of this hypothesis, namely, that male coercion is reproductively costly to victim females. The present study uses 15 years of data on inter-birth intervals from a large multilevel colony of baboons, mostly Papio h. hamadryas, with a mating system based on harem-defence polygyny to examine if male takeovers impact the length of the abducted females’ inter-birth intervals. Our analysis of 121 inter-birth intervals from 45 adult females indicates that male takeovers are reproductively costly to abducted females as they are associated with an increase in the time they take to conceive and a lengthening of the inter-birth intervals. We discuss how several factors may contribute to this reproductive cost, including male-female sexual conflict, male-male competition, and female-female competition. Our findings suggest that the male’s aggressive herding is the main contributor to the abducted females’ immediate reproductive cost. We argue that although some of the male’s aggressive herding may be driven by male-male competition, nonetheless, it serves a coercive function as it both constrains the female’s mate choice options and hampers her immediate breeding performance. This conclusion is backed up by results obtained in the only other study that has tested the same prediction and which has been carried out in a wild population of hamadryas baboons.

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Section: Discussionsupporting

confidence: 90%

Male Takeovers Are Reproductively Costly to Females in Hamadryas Baboons: A Test of the Sexual Coercion Hypothesis

2014

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“…We may have missed a few births during our longest gap in data collection, from June 2010 to the end of the year, if infants born during this period also died during this period. However, given the relatively low mortality of hamadryas infants in this population (12.9%, Swedell et al, ) it is unlikely that the number of missed births would be substantial enough to affect the outcomes of our analyses.…”

Section: Methodsmentioning

confidence: 83%

“…Gelada followers, for example, often remain with OMU females while the leader fights with male challengers (Dunbar and Dunbar, ; Mori, ), and this may help prevent loss of those females. By helping to prevent takeovers, followers also indirectly help boost infant survival because post‐takeover infant mortality in hamadryas is very high (67%, Swedell et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Follower males often interact with infants in their OMUs and may contribute to infant survival via caretaking and protective behaviors, which would supplement the limited caretaking provided by the leader male (Kummer, ; Swedell, ). Infanticide following takeovers is a pervasive threat for primate females (Hrdy, ; van Schaik and Kappeler, ), including hamadryas baboons (Swedell et al, ). It is less common in hamadryas, however, compared to other baboons (Palombit, ; Cheney et al, ; Lemasson et al, ; Henzi et al, ), and this may be a result of the protection that hamadryas females and their infants receive from both leader and follower males (Kummer, ; Swedell and Saunders, 2006).…”

mentioning

confidence: 99%

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The adaptive value of secondary males in the polygynous multi‐level society of hamadryas baboons

Chowdhury

Pines²,

Saunders³

et al. 2015

American J Phys Anthropol

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Hamadryas follower males enabled leaders to retain females for longer periods of time-likely through unit defense, social relationships with OMU members, and/or infant protection. Hamadryas leaders appear to be able to monopolize access to females despite the presence of followers, and as such any enhanced reproduction derived from the presence of followers likely increases the fitness of the leader rather than the follower. Thus the relationship between leaders and followers in hamadryas society appears to be a mutually beneficial one and tolerance of secondary males may be an adaptive reproductive strategy characterizing hamadryas leader males.

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“…44, p. 2842). Among primates with multilevel social systems (68)(69)(70), including humans (71), a male's RS usually depends on his success at claiming and retaining mates, which depends on other males deferring to his claims.…”

Section: Key Constraintsmentioning

confidence: 99%

Grandmothering life histories and human pair bonding

Coxworth

Kim

McQueen

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The evolution of distinctively human life history and social organization is generally attributed to paternal provisioning based on pair bonds. Here we develop an alternative argument that connects the evolution of human pair bonds to the male-biased mating sex ratios that accompanied the evolution of human life history. We simulate an agent-based model of the grandmother hypothesis, compare simulated sex ratios to data on great apes and human hunter-gatherers, and note associations between a preponderance of males and mate guarding across taxa. Then we explore a recent model that highlights the importance of mating sex ratios for differences between birds and mammals and conclude that lessons for human evolution cannot ignore mammalian reproductive constraints. In contradiction to our claim that male-biased sex ratios are characteristically human, female-biased ratios are reported in some populations. We consider the likelihood that fertile men are undercounted and conclude that the mate-guarding hypothesis for human pair bonds gains strength from explicit links with our grandmothering life history.grandmother hypothesis | human life history | human evolution | mate guarding | mating sex ratios W e call attention to evidence that connects the evolution of human pair bonds to the male-biased sex ratios in fertile ages that characterize human populations. As in mammals generally, age-specific mortality is higher in males than in females (e.g., refs. 1-3). However, this difference is overshadowed by a distinctive feature of human life history: Oldest ages at parturition are about the same in humans as in other living hominids, the great apes (4, 5), whereas longevity is substantially greater and male fertility continues to older ages (6). Exceptional longevity with a distinctive postmenopausal life stage (7-9) may have evolved in our lineage when grandmothers' subsidies for weaned dependents allowed mothers to have next babies sooner. According to this grandmother hypothesis (10-16), longevity increased as longer-lived grandmothers could help more and so left more longer-lived descendants of both sexes. Women's postfertile life stage (7) produces a bias in the sex ratio of fertile adults with repercussions for male strategies. As longevity increased, olderaged males expanded the pool of competitors for the still-fertile females. With more competitors for each paternity, males' average success in finding new mates inevitably declined until defending a current mate became the better option. Our distinctive life history thus supplies previously unrecognized support for a mate-guarding hypothesis for the evolution of human pair bonds.Here we simulate hominid mating sex ratios with an agent-based model of the evolution of human longevity via grandmothering (13, 15). We then compare simulated sex ratios to demographic data from both great apes and human hunter-gatherers. Having identified the human bias, we connect it to increased male payoffs for mate guarding, noting some broad patterns in humans, the tradeoffs observ...

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Sexual conflict in a polygynous primate: costs and benefits of a male-imposed mating system

Cited by 44 publications

References 73 publications

Male Takeovers Are Reproductively Costly to Females in Hamadryas Baboons: A Test of the Sexual Coercion Hypothesis

Male Takeovers Are Reproductively Costly to Females in Hamadryas Baboons: A Test of the Sexual Coercion Hypothesis

The adaptive value of secondary males in the polygynous multi‐level society of hamadryas baboons

Grandmothering life histories and human pair bonding

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