Within-group female-female agonistic interactions in Taiwanese macaques (Macaca cyclopis)

Feeding-related agonism among wild female Taiwanese macaques was investigated in two study groups at ecologically diverse sites (Fu-shan and Ken-ting) to determine whether contest-feeding competition was present in these groups. Females that contest for food within a primate group are hypothesized to form dominance hierarchies and tend to be philopatric. In this study we tested 1) whether Taiwanese macaque females show higher agonism in a feeding context, 2) whether they exhibit stronger agonism over higher-quality foods, and 3) whether higher agonism rates occur in smaller food patches. Female Taiwanese macaques at both study sites showed similar agonism rates in a feeding context (0.30 events/hr). They exhibited higher agonism rates inside food patches than outside food patches in the spring. Higher agonism rates occurred during seasons of higher fruit availability, and a lower agonism rate occurred in winter when the macaques switched to feeding on fallback foods. Females in the Fu-shan group exhibited higher proportions of aggressive interactions over higher-quality foods, such as animal matter and the reproductive parts of plants. In the Ken-ting group, 95.8% of feeding-related agonistic interactions among females occurred over fruits. Agonistic interactions that occurred in small food patches tended to result in the agonism recipient leaving the food patch. We conclude that female Taiwanese macaques show contest feeding competition in certain contexts. The patterns we observed have also been documented in other primate species in which females are philopatric and form linear dominance hierarchies.