Seasonal variation in feeding behavior, competition and female social relationships in a forest dwelling guenon, the blue monkey (Cercopithecus mitis stuhlmanni), in the Kakamega Forest, Kenya

Socioecological models relate differences in feeding strategies to variation in the nature of female social relationships. Among the African forest guenons, females consume large quantities of fruit and other plant reproductive parts, resources which are thought to promote contest competition, yet these monkeys have been characterized as having agonistically undifferentiated relationships in which rank, if discernible at all, does not correlate with fitness benefits. To determine whether female relationships become more hierarchical under relevant ecological conditions, we monitored the adult females of two blue monkey groups (Cercopithecus mitis stuhlmanni) over a complete annual cycle in the Kakamega Forest, Kenya. Females competed aggressively for plant reproductive parts more often than any other resource type, and in both groups we detected linear dominance hierarchies. Nonetheless, agonism rates remained low throughout our study, and did not vary with changes in ecological conditions. Rather, when plant reproductive parts were scarce, subordinate females spent more time feeding and less time resting in an apparent attempt to compensate for a reduced efficiency of food intake. The effects of rank and food abundance were not reflected, however, in the distribution of grooming. The use of alternative feeding strategies appeared to blunt competition – females of all ranks were unlikely to be near others while feeding and spent more time consuming alternative resources when plant reproductive parts were scarce. The diverse diet of this species may allow females to avoid conflict so that dominance has only subtle effects that are difficult to detect. While socioecological models often simplify the connection between resources and female interactions, our results emphasize that the behavior of animals consuming particular resources, and not the resources themselves, are critical predictors of social patterns.