Absence of 'Youngest Ascendancy' in the Dominance Relations of Sisters in Wild Japanese Macaques (Macaca Fuscata Yakui)

AbstractDominance relations among females were studied in a small, well-habituated troop of Yakushima macaques (Macaca fuscata yakuz) in southernjapan. Data were collected using focal animal sampling over a 20-month period. Although the frequency of aggression was much lower than that reported for provisioned groups, and support in agonistic interactions was rare, a clear linear dominance hierarchy was apparent. In each of the four pairs of sisters in the troop the older was dominant to the younger. This is contrary to the pattern commonly reported for provisioned groups of Japanese and rhesus macaques, in which dominance among sexually mature sisters tends to be inversely correlated with age. For each pair of sisters in the study troop the mother was alive and healthy when the younger daughter became sexually active, but no cases were seen of a mother aiding one daughter against another. We therefore conclude a) that the absence of youngest ascendancy was due to a lack of support, rather than a lack of potential allies, and b) that both frequent agonistic support and youngest ascendancy are most likely to occur under conditions where concentrated food resources result in frequent and intense aggression.