Patterns of Dominance Relationships among the Females of a Captive Femaleonly Group of Lion-Tailed Macaques (Macaca silenus) during the Course of the Introduction of a New Adult Male

Lion-tailed macaques are generally considered to have more despotic than egalitarian dominance relationships; however, research lacks any conclusive evidence. In the present study, we examined dominance relationships among the females (of which the genealogical relationships were known) of a captive female-only group of lion-tailed macaques (Macaca silenus) during the course of introduction of a new adult male to the group at the Wels Zoo, Wels, Austria. We determined the structure of dominance hierarchy and the corresponding changes in dominance relationships, possibly mediated by an increase in sexual competition among the females. When the females were housed together without any adult male for over four months following the death of the former breeding male, the dominance hierarchy almost followed the principle of youngest ascendency. When a new male was housed for 26 days in an enclosure adjacent to that of the females (such that the females and the new male could interact with each other through a wire mesh between their enclosures), changes in dominance hierarchy were observed. During this phase, there was a temporary change in the dominance hierarchy, leading to a higher degree of aggression of the nursing female and an increase in its dominance rank. This is corroborated by the fact that when the new male was housed together with the females in the same enclosure, it resulted in infanticide and subsequently, the nursing mother lost the higher rank. We consider the implications of the present study in the captive management and breeding of long-tailed macaque.