| During the long term of evolution,group living animals formed multiple social system to face the challenge of environmental change.As one of the most evolved mammals,primates formed a complex social system,which is the multilevel society.In past decades,researchers studied the pattern of this social system,and raised two hypothesis of its evolutionary pathway.To test these hypothesis,further study on the specific mechanism and social dynamic of each layers of the multilevel society is required.In this thesis,we choose wild golden snub-nosed monkeys as the study subject.By building a long term database of demographic change,and using the methods of social network and genetic analysis,we purpose to research the specific mechanism of social stability,and also the social dynamics of the multilevel society in golden snub-nosed monkeys.We raised the following hypothesis: 1)female dispersal maintains the affiliation among breeding units;2)kin-based recruitment plays an important role during the formation of all male units;3)complex social structure enables individuals to employ multiple behavioral strategies,for instance,the delay-dispersal of male offspring and male-male mounting behaviour.The main results are list below.1.By using social network analysis and liner mix model,we found that among all the facts(unit size,hierarchy,demographic change),the females transfer among different units significantly influences the cluster coefficient(LMM: p < 0.001).Also,genetic matrices were significantly correlated with behavioral matrices(MRQAP: p = 0.000).Results suggested that the females' kinship is the reason of the close relationship in behaviour among units.With close female kinship,units are more likely to have close spatial proximity.These results suggest that the kin selection could be the main factor of the social stability in breeding band of golden snub-nosed monkeys.2.Natal dispersals are male-biased in most Old World monkey species,especially those that are polygynous.We examined patterns of male dispersal in golden snub-nosed monkeys,in which male offspring mainly disperse as juveniles from their natal one-male units(OMUs)to a bachelor group.However,out of a total of 112 male dispersals from 2001–2016,we documented six cases in which male offspring remained in their natal OMU until sub-adulthood.Based on monitoring of dispersal dynamics,we found that male offspring were more likely to delay dispersal if the tenure of leader males was lengthy.Social network analysis showed male offspring who delayed dispersal exhibited strong social relationships with each other and their OMU leader male but not with the females of their OMU.Our results suggest that the length of leader male tenure may affect natal male dispersal due to benefits to leader males accrued via intrasexual competition and kin selection.Complex social system enables males to employ alternative reproductive tactics.3.Social relationship of male-male bond in mammals are tend to be competitive and aggressive.However,in most primate with multilevel society,males form all male groups,providing opportunities for strong male-male bonds to emerge.Based on combination of social network analysis and genetic investigation,we observed and examined the immigration of an ouster male to all-male groups,and assessed the possible factors both from ethological and genetic aspect.The results show that the immigration led to the formation of a new union in all male group,and also represent a significant genetic relatedness within the newly formed unit when compared to the rest.Marginal individuals were more inclined to be recruited.Our data indicated an initiated adult bachelor male basically based on kinship,and also are related to social relations.The cooperation strategies of marginal individuals as well have important functions in the formation of new unit.4.We collect data on the frequencies and contextual significance of male-male mounting behaviour.Mounts occurred in a variety of affiliative,dominance-related and sexual contexts,which differed depending upon the ages of the males involved.Mounting behaviour in this group was mainly initiated by adults.Juveniles mounted each other in affiliative contexts(during play and prior to grooming).Adult males mounted subadult and juvenile partners in a greater variety of sociosexual contexts(dominance/rank-related interactions;reconciliation following agonistic encounters,and sometimes as a prelude to receiving grooming).However,subadults and juveniles were never observed to mount adults.In one dyad,involving an adult male and a subadult partner,mounting was more frequent and prolonged,and included bouts of deep pelvic thrusting.Two mounts resulted in anal intromissions and,in 1 case,the subadult partner exhibited seminal emission.It is possible that this unusual male-male sexual activity was related to the absence of mating opportunitiesIn conclusion,kin selection plays an important role in both breeding band and all male band of golden snub-nosed monkeys.The kinship of females among units significantly influences the social affiliation of the units;while the kin-based recruitment promotes the establishment of unit in all male band.Golden snub-nosed monkeys evolved to varies behavioural strategies under the complex social system,including the delay-dispersal and male-male mounting behaviour,which could be the potential social dynamics of multilevel society. |
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