Abstract # 13:

Scheduled for Saturday, September 17, 2011 09:15 AM-09:30 AM: Session 4 (Meeting Room 410) Oral Presentation


A NEW FORM OF SOCIAL ORGANIZATION IN AN ASIAN COLOBINE

A. Koenig and C. Borries
Stony Brook University, Department of Anthropology, Stony Brook, NY 11794-4364, USA
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In many primates, female group size and receptivity overlap are strong predictors of the number of males in a group. In contrast, the genus Trachypithecus is characterized by one-male groups of different sizes and occasional age-graded multimale groups. Male membership mainly changes via immigrations or take-overs. Here we investigate the relationship between male and female numbers, the dispersal pattern, and the occurrence of multimale groups in Phayre's leaf monkeys (Trachypithecus phayrei crepusculus) in Thailand. Behavioral and demographic data were collected for 4 groups over 23.3 group-years. We found a high prevalence of multimale groups (51.5%), while group size (mean: 19.5, range: 6-33) fell within the range reported for the genus. The number of males was not affected by the number of females (mixed model ANOVA: F=0.19, p=0.675). Male immigrations or take-overs were not observed. Rather, males matured and bred in their natal group (n=8), disappeared (n=15), or formed new groups (2 events, 4 males each). Multimale groups were not age-graded, but maturing males occupied the top ranks. These results suggest a new social organization among Asian colobines, in which males mature and breed in their natal group or disperse and form new groups. Multimale and one-male groups are equally likely phases within a dynamic social organization. Supported by NSF (BCS-0215542, BCS-0542035), Leakey Foundation, and Stony Brook University.