Male mating strategies in a fluid social system: Dunbar’s general model of mating strategies revisited

Dunbar’s general model of mating strategies provides a useful, but largely ignored approach for understanding the fundamental choice faced by male: to remain with females in order to exploit paternity opportunities when they arise, a social strategy, or to search for these opportunities on an ongoing, roving, basis. The model has been criticized in both its assumptions, and the data used to test it. Using published data from six different communities of chimpanzees, we address three questions: How robust is Dunbar’s original model; how robust is its support for social males in West and roving males in East Africa; and how real are supposed differences in female gregariousness between West and East African chimpanzees? We test the original model against two variants and find that despite quantitative differences, all three generate the same qualitative prediction. Thus for chimpanzees at least, Dunbar’s original model can be regarded as fairly robust. However, this prediction is that chimpanzee males should pursue a ‘roving’ strategy and that this was as true for West as for East African chimpanzees. Furthermore, the comparative data did not support an East/West dichotomy in female gregariousness. This study highlights the importance of the collection and reporting of comparable data, the utility of simple mathematical models, and the similarities in behaviour across subspecies of chimpanzees.