Abstract # 16:

Scheduled for Saturday, September 17, 2011 10:00 AM-10:15 AM: Session 4 (Meeting Room 410) Oral Presentation


W. M. Erb1, C. Borries2, N. S. Lestari3 and T. Ziegler4
1Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, NY 11794-4364, USA, 2Department of Anthropology, Stony Brook University, 3Forest Research and Development Agency, Ministry of Forestry, Indonesia, 4Siberut Conservation Programme, German Primate Center, Germany
     Asian colobines typically live in small one-male units (OMUs) averaging 5 adult females. Simakobu (Simias concolor) are often considered an exception because mostly adult pairs have been reported. However, based on phylogeny and the degree of sexual dimorphism, Simakobu are predicted to form one-male polygynous groups. Thus, the predominance of small groups could have been the result of human disturbance (hunting or habitat alteration) reducing relative numbers of adults and/or immatures in the recent past. To investigate this, we documented the demography of 10 wild Simakobu groups during 26 months at an undisturbed site, the Peleonan Forest, Siberut, Indonesia. We assessed group size and composition, and demographic changes in groups over time. We found OMUs with 3.0 adult females on average as well as all-male units, but no adult pairs. Both male and female dispersal occurred, and juveniles seemed to disperse most frequently. Next, we used regressions to compare demographic data from six Simakobu populations. Both the number of adult females and the number of immatures were negatively impacted by hunting (P<0.01) and positively impacted by habitat alteration (P<0.05), while the ratio of immatures to adult females was not affected by either disturbance measure. Our results suggest that the adult pairs observed in some populations are a result of hunting pressure reducing group size. Supported by CI, PCI, ASP, and NSF DDIG (BCS-0752504).