Doctoral Dissertation Improvement: Comparative Positional Behavior of Asian Hominoidea.

Southern Illinois University At Carbondale, Carbondale IL

Investigators

Abstract

Body size is a major constraint in the arboreal milieu, and orthograde (upright) locomotor and postural behaviors are thought to have conveyed substantial advantages to the evolutionary development of the relatively large-bodied apes (hominoids). The results from this study will expand the current understanding of hominoid, especially gibbon, positional behavior. Additionally, as resource competitors of the critically endangered Sumatran orangutan, data on the positional behavior, forest use, and feeding/foraging strategies of endangered sympatric gibbons represents a key component to the conservation strategies at West Batang Toro, North Sumatra, Indonesia (WBT). This study also integrates with a larger project on the biodiversity of WBT, involving local and international researchers with diverse specializations, and will therefore also facilitate cross-national and inter-disciplinary ties. Lastly, the Co-PI will help educate Indonesian students and surrounding local communities about WBT and its ecological benefits. While studies have addressed how body size and positional behavior covary among the largest representatives of this taxonomic group, far less has been reported on this relationship for the small-bodied hylobatids. This is particularly interesting as these anatomically and behaviorally specialized primates are thought to represent a lineage that has evolutionarily reduced in body size and fine-tuned the ape pattern of generalized orthogrady in order to more efficiently exploit the arboreal canopy. As a test of this hypothesis, the relationships between body size, habitat use, and positional behavior of size-variable sympatric gibbons (Hylobates agilis) and siamangs (Symphalangus syndactylus) are examined at WBT. Previously collected data by the Co-PI for Hylobates lar from Khao Yai National Park, Thailand is also used for comparison. Additionally, data from this study are compared with previously published data for other hominoids, atelids, cebids, and cercopithecoids in order to reevaluate ape locomotor and postural specializations.