Reproductive Competition Among Males in Multimale Groups of Primates: Modeling the Costs and Effectiveness of Conflict
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Multimale groups of primates are characterized by strong reproductive competition among males, generally resulting in an uneven division of male reproductive success (reproductive skew). The observed patterns of conflict and reproductive skew have often been attributed to the so-called tug-of-war model. We show, however, that two important assumptions of this model are not met in male primates. First, the tug-of-war model assumes that reproductive conflict reduces overall group productivity, but in male primates (and most other vertebrates) conflict likely involves mortality rather than fecundity costs. Second, the tug-of-war model does not account for the possibility that male primates can achieve some reproductive success without engagement in open conflict, such as when a single male cannot guard several receptive females at the same time. We therefore develop a dynamic version of the tug-of-war model, in which reproductive competition causes mortality costs, and in which individuals can gain uncontested shares of reproduction dependent on the degree of female receptive overlap. This model differs substantially from the original tug-of-war model, and derives a new and rich set of comparative predictions. For instance, it predicts that the level of conflict among males declines as the queuing success of subordinate males increases (as survival increases), and also, as their uncontested share of reproduction increases, e.g., as female receptive overlap increases. Our model shows how male–male conflict and female receptive overlap collectively determine the level of reproductive skew among male primates, and illustrates that this relationship is more complex than previously thought.
KeywordsQueuing Priority of access Reproductive skew Social conflict Tug-of-war
We thank Alexander Georgiev and Melissa Emery Thompson for inviting us to contribute to this special issue of International Journal of Primatology. We thank Rufus Johnstone, A. Georgiev, M. E. Thompson, Joanna Setchell, and three anonymous reviewers for valuable comments on this manuscript. M. Port was supported by a grant from the VolkswagenStiftung.
- Bradley, B. J., Robbins, M. M., Williamson, E. A., Steklis, H. D., Steklis, N. G., Eckhardt, N., Boesch, C., & Vigilant, L. (2005). Mountain gorilla tug-of-war: Silverbacks have limited control over reproduction in multimale groups. Proceedings of the National Academy of Sciences of the USA, 102, 9418–9423.PubMedCentralPubMedCrossRefGoogle Scholar
- Clutton-Brock, T. H., Brotherton, P. N. M., Smith, R., McIlrath, G. M., Kansky, R., Gaynor, D., O'Riain, M. J., & Skinner, J. D. (1998). Infanticide and expulsion of females in a cooperatively breeding mammal. Proceedings of the Royal Society of London B: Biological Sciences, 265, 2291–2295.CrossRefGoogle Scholar
- Henzi, S.P., Clarke, P.M.R., van Schaik, C.P., Pradhan, G.R., & Barrett, L. (2010). Infanticide and reproductive restraint in a polygynous social mammal. Proceedings of the National Academy of Sciences of the USA, 107, 2130-2135.Google Scholar
- Nonacs, P. (2006). The rise and fall of transactional skew theory in the model genus Polistes. Annales Zoologici Fenniciis, 43, 443–455.Google Scholar
- Plavcan, J. M., & van Schaik, C. P. (1997). Intrasexual competition and body weight dimorphism in anthropoid primates. American Journal of Physical Anthropology, 103, 37–67.Google Scholar
- Port, M., & Cant, M. A. (2013). Longevity suppresses conflict in animal societies. Biology Letters. doi: 10.1098/rsbl.2013.0680.
- Reeve, H. K., & Ratniecks, F. L. W. (1993). Queen-queen conflict in polygynous societies: Mutual tolerance and reproductive skew. In L. Keller (Ed.), Queen number and sociality in insects (pp. 45–85). Oxford: Oxford University Press.Google Scholar
- Röseler, P. F. (1991). Reproductive competition during colony establishment. In K. G. Ross & R. W. Matthews (Eds.), The social biology of wasps (pp. 309–335). Ithaca, NY: Cornell University Press.Google Scholar
- Vehrencamp, S. L. (1983a). Optimal degree of skew in cooperative societies. American Zoologist, 23, 327–335.Google Scholar
- Young, A. J., Carlson, A. A., Monfort, S., Russell, A. F., Bennett, N. C., & Clutton-Brock, T. H. (2006). Stress and the suppression of sobordinate reproduction in cooperatively breeding meerkats. Proceedings of the National Academy of Sciences of the USA, 103, 12005–12010.PubMedCentralPubMedCrossRefGoogle Scholar