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Metahāra, Ethiopia

Pines M.,Filoha Hamadryas Project | Swedell L.,New York University
American Journal of Primatology | Year: 2016

In many social animals, individuals derive fitness benefits from close social bonds, which are often formed among kin of the philopatric sex. Hamadryas baboons, however, exhibit a hierarchical, multilevel social system where both sexes disperse from their natal one-male-unit (OMU). Although this would seem to hinder maintenance of kin ties, both sexes appear largely philopatric at the higher order band and clan levels, possibly allowing for bonds with same sex kin by both males and females. In order to investigate the possibility of kin bonds in hamadryas baboons, we identified kin dyads in a band without known pedigree information using a large panel of genetic markers: 1 Y-linked, 4 X-linked, and 23 autosomal microsatellites and part of the mitochondrial hypervariable region I. With these data, we performed a kinship analysis while accounting for misclassification rates through simulations and determined kinship among two types of dyads: leader and follower males and female dyads within OMUs. Leader and follower males were maternal relatives more often than expected by chance, suggesting that kinship plays a role in the formation of these relationships. Moreover, maternal female relatives were found in the same OMU more often than expected by chance, indicating that females may be motivated to maintain post-dispersal contact with maternal female kin. Our results suggest that hamadryas baboons can recognize maternal kin and that kin selection has contributed to shaping their complex social system. This implies that an ancestral maternal kin bias has been retained in hamadryas society. © 2016 Wiley Periodicals, Inc. Source


Pines M.,Filoha Hamadryas Project | Saunders J.,Filoha Hamadryas Project | Saunders J.,University of Cape Town | Swedell L.,Filoha Hamadryas Project | And 2 more authors.
American Journal of Primatology | Year: 2011

The nested one-male units (OMUs) of the hamadryas baboon are part of a complex social system in which "leader" males achieve near exclusive mating access by forcibly herding females into permanent consortships. Within this multi-level social system (troops, bands, clans and OMUs) are two types of prereproductive males-the follower and solitary male-whose different trajectories converge on the leader role. Here we compare OMU formation strategies of followers, who associate with a particular OMU and may have social access to females, with those of solitary males, who move freely within the band and do not associate regularly with OMUs. Data were derived from 42 OMU formations (16 by followers and 26 by solitary males) occurring over 8 years in a hamadryas baboon band at the Filoha site in Ethiopia. "Initial units" (IUs) with sexually immature females (IU strategy) were formed by 44% of followers and 46% of solitary males. The remaining followers took over mature females when their leader was deposed (challenge strategy) or disappeared (opportunistic strategy), or via a seemingly peaceful transfer (inheritance strategy). Solitary males took over mature females from other clans and bands, but mainly from old, injured or vanished leaders within their clan (via both the challenge and opportunistic strategies). Former followers of an OMU were more successful at taking over females from those OMUs than any other category of male. Despite this advantage enjoyed by ex-follower leaders, ex-solitary leaders were equally capable of increasing their OMU size at a comparable rate in their first 2 years as a leader. These results demonstrate the potential for males to employ both multiple roles (follower vs. solitary male) and multiple routes (IU, inheritance, challenge, opportunistic) to acquire females and become a leader male in a mating system characterized by female defense polygyny in a competitive arena. © 2011 Wiley-Liss, Inc. Source


Pines M.,Filoha Hamadryas Project | Swedell L.,Filoha Hamadryas Project | Swedell L.,Queens College, City University of New York
Primates | Year: 2011

In contrast to other papionin monkeys, hamadryas baboons are characterized by female-biased dispersal. Given that hamadryas females do not disperse voluntarily, one mechanism for female transfer between bands is thought to be abductions during aggressive intergroup conflict. To date, however, no successful abductions have been witnessed. We describe three abduction events at the Filoha field site in Ethiopia, two interband and one intraband, in which the abductors successfully separated a female from her leader male for several minutes or hours. In each case, the original leader male located the abductor and retrieved the female, even if it involved entering the social sphere of another band. These observations suggest that a hamadryas leader male will risk injury and loss of additional females in his attempt to retrieve a female from an abductor unless the abductor has openly challenged the leader for possession of his female and physically defeated him. © 2011 Japan Monkey Centre and Springer. Source


Swedell L.,Queens College, City University of New York | Swedell L.,University of Cape Town | Leedom L.,University of Bridgeport | Saunders J.,Filoha Hamadryas Project | Pines M.,Filoha Hamadryas Project
Behavioral Ecology and Sociobiology | Year: 2013

Fundamental reproductive interests dictate that females generally benefit most from mate selectivity and males from mate quantity. This can create conflict between the sexes and result in sexual coercion: male use of aggression to garner mating success at a cost to females. Potential fitness costs of sexual coercion, however, can be difficult to measure. Here, we demonstrate benefits to males and costs to females of female defense polygyny in wild hamadryas baboons, cercopithecoid primates in which females are coercively transferred among social units by males, restricting both female choice and bonding among female kin. Of all coercive transfers (takeovers) of females with young infants, 67%were followed by infant mortality, which was significantly more likely to occur after takeovers than at other times. As expected, infant mortality decreased time to subsequent conception but lengthened intervals between surviving infants. Following infant survival, whether a female had experienced a takeover after the previous birth was a significant predictor of subsequent interbirth interval, with interbirth intervals of females remaining with the same male between births being significantly shorter than those of females incurring takeovers between births. Together, these results reveal that takeovers increase the chance of infant mortality while delaying subsequent conception. Maledriven female defense polygyny in this species is thus costly to females in two ways. These results demonstrate that reproductive strategies benefitting males can evolve despite substantial costs to females. These costs may be mitigated over the long term, however, by female counterstrategies and protective behavior by males. © 2013, Springer-Verlag Berlin Heidelberg. Source


Chowdhury S.,City University of New York | Chowdhury S.,Queens College, City University of New York | Pines M.,Filoha Hamadryas Project | Saunders J.,Filoha Hamadryas Project | And 3 more authors.
American Journal of Physical Anthropology | Year: 2015

Objectives One-male social systems are usually characterized by polygyny and reproductive exclusion by a single resident male. Sometimes, however, secondary males join these groups, and this may carry fitness costs and/or benefits to the resident male. In hamadryas baboons (Papio hamadryas hamadryas), which live in one-male units (OMUs) with female defense polygyny within a multi-level social system, secondary "follower" males often reside in OMUs. Our aim here is to examine possible benefits of these secondary males to hamadryas resident males. Materials and Methods Using 6 years of data from 65 OMUs in a band of wild hamadryas baboons in Ethiopia, we compared demographic and reproductive parameters of OMUs with and without secondary "follower" males to assess whether their presence conferred any reproductive benefits to resident "leader" males. Results Leaders with followers had tenure lengths almost twice as long, acquired more than twice as many females, retained females longer, and had three times as many infants during their tenure compared to leaders without followers. Discussion 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. Am J Phys Anthropol 158:501-513, 2015. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc. Source

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