Genetic relatedness in two-tiered plains zebra societies suggests that females choose to associate with kin

in Behaviour
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How kinship structures alter inclusive fitness benefits or competition costs to members of a group can explain variation in animal societies. We present rare data combining behavioural associations and genetic relatedness to determine the influence of sex differences and kinship in structuring a two-tiered zebra society. We found a significantly positive relationship between the strength of behavioural association and relatedness. Female relatedness within herds was higher than chance, suggesting that female kin drive herd formation, and consistent with evidence that lactating females preferentially group into herds to dilute predation risk. In contrast, male relatedness across harems in a herd was no different from relatedness across herds, suggesting that although stallions benefit from associating to fend off bachelors, they do not preferentially form kin coalitions. Although both sexes disperse, we found that most harems contained adult relatives, implying limited female dispersal distances and inbreeding in this population, with potential conservation consequences.

Genetic relatedness in two-tiered plains zebra societies suggests that females choose to associate with kin

in Behaviour



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    Graph of pairwise association index against pairwise genetic relatedness for all sampled zebra dyads in the Sweetwaters population, with quadratic regression line and shaded 95% confidence intervals. Dyads that are observed interacting as estimated by the association index are significantly more likely to be genetic relatives. An association index of zero indicates that a dyad of individuals was never seen together, while an index of one indicates that every time two individuals were seen, they were observed together in close proximity. Zero genetic relatedness is expected if a dyad of individuals does not share any alleles, while 0.5 is expected for first order relatives.

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    Pairwise relatedness between members of herds and harems in the Sweetwaters Game Reserve. Females are peach, stallions blue, bachelors pale blue and the only female juvenile is yellow. Harems are enclosed by ovals, while herds are enclosed by rectangles. Only relatedness scores > 0.1 are represented, and line thickness joining individuals indicates the strength of relatedness. This figure is published in colour in the online edition of this journal, which can be accessed via

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