Abstract # 139:

Scheduled for Friday, August 18, 2006 04:00 PM-04:15 PM: Session 14 (Regency East #2) Oral Presentation

Variation in and constraints on group size in platyrrhines

M. A. Norconk, E. E. Henthorn and R. S. Meindl
Kent State University, Dept. of Anthropology, School of Biomedical Sciences, 228 Lowry Hall, Kent, OH 44242, USA
     Monkeys are found in group sizes that range from six to more than 400 individuals. While sources of within-species or between-population variation have received considerable interest, inter-specific variation is less frequently the point of departure for these studies. In the first step of this analysis, we found that New World monkeys live in much smaller groups than Old World monkeys. We then collected data on group composition from published sources and added data on body mass and number of breeding females. In all, we developed eight raw and composite variables from 60 species of platyrrhines and 64 species of cercopithecids. Since some genera in both New World and Old World radiations are highly speciose, we used the genus average as our unit of comparison. The first principal component accounted for 52.2% of the variance and reflected primarily body mass incorporated in several ways: sexual dimorphism, female body mass and group mass. However, the variable "number of breeding females" in a group was an equally strong predictor of group size. Callitrichines plus Aotus, Pithecia, and Callicebus clustered together and the other cebids were intermixed with cercopithecids. In this analysis, most of the smallest New World monkeys show a pattern of small group size and limitations on the number of breeding females that is different from other platyrrhines and Old World monkeys.