Abstract # 56:

Scheduled for Thursday, June 17, 2010 07:00 PM-09:00 PM: Session 11 (Medallion Ballroom C/D/E/F) Poster Presentation


THE INFLUENCE OF AGE AND RANK ON THE VOCALIZATIONS OF MALE MOUNTAIN GORILLAS (GORILLA BERINGEI BERINGEI) LIVING IN MULTI-MALE GROUPS

T. S. Stoinski1,2, S. Keenan2, S. Rosenbaum3 and K. Fawcett1
1The Dian Fossey Gorilla Fund, 800 Cherokee Ave. SE, Atlanta, GA 30315-1440, USA, 2Zoo Atlanta, 3UCLA
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The current study addressed how rank and age affected patterns of close calling among male mountain gorillas living in large, multi-male groups. Subjects included 27 males (>8 years) living in three multi-male/multi-female groups monitored by the Karisoke Research Center. Focal animal sampling [n=505 hours] was used to record the frequency of syllabeled close calls (e.g., grunts, double grunts). For calls that were part of a vocal exchange, we also recorded if the focal was the initiator or respondent and, when the initiator, if one or more than one other group member responded. Rank was determined as in Stoinski et al. (2009); the top three ranking males within a group were classified as dominant and the remaining as subordinant. A GLM with rank as a fixed factor and age and group as covariates found significant effects of age and rank. Silverbacks (>12 years) vocalized at four times the rate of blackbacks [<12 years; P<0.05]; their higher rates of vocalizing resulted from greater vocal exchanges. Dominants did not vocalize at higher rates than subordinants but were more likely to produce calls that elicited a response [P< 0.05] and to have multiple individuals respond to their calls [P=0.05]. The data are the first to look at vocalization patterns in groups with large numbers of males and suggest such patterns may be a tool for determining dominance.