Ramesh Boonratana Mahidol University A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy (Biology) In Faculty of Graduate Studies Mahidol University 1993 ABSTRACT Nasalis larvatus is a large, sexually dimorphic, monotypic arboreal colobine, endemic to the island of Borneo, where it is largely restricted to riverine, peat swamp and mangrove forests of the coastal lowlands. The aims of the study were to assess the ecology and behavior of N. larvatus in relation to the botany and phytochemistry of the habitat flora. This involved two years field work in the mangrove and riverine forests in the Lower Kinabatangan area. The basic social unit of N. larvatus relatively stable harem, comprising a single adult male, several adult females and their offspring. The Social structure of N. larvatus in the Lower Kinabatangan is flexible, and comprised relatively stable harem, all-male and predominantly male non-breeding groups. Different groups frequently selected riverside sleeping sites that were close to one another. Some groups associated more than others, implying a secondary level of social organisation, the band. Intra-group agonistic and social interactions were rare, implying that intra-group competition was low. This, in turn suggested that food was abundant and available. All colobines, including N. larvatus, possess specialised digestive physiology and sacculated stomachs with anaerobic, cellulolytic bacteria in their fore-stomachs. This adaptation allows them to break down cell wall constituents and defensive chemicals found in plant foods. N. larvatus is a folivore-frugivore, with a strong preference for seeds-. They are highly selective feeders, avoiding items with high levels of digestion inhibitors. Nasalis larvatus groups in the Lower Kinabatangan were wide-ranging, returning to sleep by the Kinabatangan River or its tributaries every evening. N. larvatus are not territorial, and the ranges of different groups completely overlapped each other. The home range size of the focal harem group, SU1, at Sukau was observed to be 221 ha. SU1 increased its day range lengths as high quality foods become scarcer, and the group selected particular quadrats on days when its members ate high quality foods. This suggested that food resources were unevenly distributed and highly clumped. Differences in home range size, group size, population density of N. larvatus between sites, and the fact that groups were non-territorial, with completely overlapping ranges and low level of intra-group interactions, strongly implied that these variable were influenced by ecological pressures, particularly by the distribution, size and abundance of food resources. TABLE OF CONTENTS 1. Introduction 1 2. Methods 18 3. Study Area 42 4. Social Organization and Behavior 79 5. Feeding Ecology 141 6. Ranging Behaviour 182 7. Concluding Discussion 212 Appendix Literature Cited HOW TO BORROW: To borrow this document, contact Joanne Brown (brown@primate.wisc.edu), Head of Technical Services, Wisconsin Regional Primate Research Center Library and Information Service, University of Wisconsin-Madison. Fax: 1-608-263-3512 Note: The Wisconsin Primate Research Center Library and Information Service welcomes announcement copies of theses dealing with nonhuman primate topics. Please send one copy to: Primate Science Coordinator, Wisconsin Primate Research Center, University of Wisconsin, 1220 Capitol Court, Madison, WI 53715. We can loan your thesis to interested users from our collection or you can provide a cost to obtain. All theses will be announced on Primate-Science and posted in Book Received on Primate Info Net. Please consider putting a depository copy at the Wisconsin Center which can be made available to the research community. Posted Date: 2-11-03
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