Correlations of food distribution and patch size with agonistic interactions in female vervets ( Chlorocebus aethiops ) and patas monkeys ( Erythrocebus patas ) living in simple habitats

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Food distribution is hypothesized to be impor- tant in determining the nature of female relationships within social groups of primates. When food limits fe- male reproductive success, spatially clumped foods are expected to produce strong, linear dominance hierarchies within groups, whereas more spatially dispersed foods are expected to produce weaker or non-existent domi- nance hierarchies. The association between food distri- bution and competitive relationships presumably occurs because clumped foods are usurpable but dispersed foods are not. We examined the spatial distribution of food patches (trees) and patch size relative to feeding be- havior and agonistic interactions in vervets and patas monkeys, two closely related and sympatric species that nonetheless differ in the strength of the female domi- nance hierarchy. Food patches of both patas monkeys and vervets were small in size and randomly distributed in Acacia drepanolobium habitat. In contrast, in A. xanthophloea woodland, the habitat type that was exclu- sively used by vervets, food patches were larger and more spatially clumped. These similarities and differ- ences between and within species were correlated with similarities and differences in the strength and linearity of their dominance hierarchies. Patas monkeys and ver- vets in A. drepanolobium habitat had dominance hierar- chies that were weakly defined because there were rela- tively few agonistic interactions between females. By contrast, in A. xanthophloea habitat, vervets had a stronger, linear dominance hierarchy characterized by a higher rate of agonistic interactions over food. The co- variation of agonistic interactions with patch size is dis- cussed in relation to depletion time, another characteris- tic that may covary with food distribution, and resource renewal rate, an important determinant of agonistic inter- actions in insectivorous birds, fishes, insects, and mam- mals.