The socio-ecology of the black-shanked douc (Pygathrix nigripes) in Mondulkiri Province, Cambodia

Abstract

This thesis details research into the ecology and behaviour of the black-shanked douc (Pygathrix nigripes Milne-Edwards, 1871), an Endangered colobine found in eastern Cambodia and southern Vietnam. The study was conducted in Seima Biodiversity Conservation Area (SBCA), Mondulkiri Province, Cambodia, over a period of 20 months, from January 2003 to August 2004, and therefore represents the longest-term study of any species in the genus. Distributional and relative density data show that black-shanked doucs preferentially utilise evergreen forest. There they maintain the largest group sizes and highest relative densities. The species is also commonly found in semi-evergreen and mixed deciduous forest, although the latter may be sub-optimal due to limited food resources. P. nigripes additionally occurs in dry deciduous dipterocarp forest but probably only where it is associated with one of the first three forest types. Group sizes appear to be lower in suboptimal habitats as suggested by the ecological constraints model. Four major social units occur in the species: one-male units (OMUs), bands comprised of several OMUs, bachelor groups and lone males. OMUs averaged 7.5 individuals, and were composed of a single male, several females and offspring. Black-shanked doucs have a fission-fusion social system, with fusion of OMUs into bands occurring more commonly in the wet season. The maximum band size recorded was 26 individuals. Activity budgets were similar to other colobine species. Inactivity dominated with a frequency of 61%, feeding 27%, travel 6%, social behaviour 3%, and other activities 2%. Daily distribution of activities was also a typically colobine pattern with high rates of feeding in the morning, a long midday period of inactivity followed by a second feeding bout in the afternoon. Locomotion was predominantly quadrupedal although frequencies of brachiation were significant. The majority of activities occurred in the middle to upper forest canopy: only one instance of terrestriality was recorded. Several behaviours not previously documented in wild doucs were observed, including paternalistic behaviour and allomothering. Contrary to previous studies on the feeding ecology of Pygathrix, P. nigripes at the site was best characterised as a seed predator, with 40% of feeding records being dedicated to seeds. Leaves, especially young leaves, also comprised a significant part of the diet.Doucs were highly selective in their diet, feeding from only 35 positively-identified plant species and with 44% of all feeding records coming from only five species. Legume species were heavily targeted. Diets did not track resource abundance across seasons with the exception of high levels of flower consumption correlated with high availability during the dry season and seed consumption during the wet season. SBCA holds the largest known population of the species across its range and is under active conservation management by the Wildlife Conservation Society and the Forestry Administration of the Royal Government of Cambodia and therefore represents one of the best opportunities for long-term conservation of the species. Having an understanding of habitat preferences, feeding ecology and behaviour as presented in this thesis provides a basis for management of the species at this site and beyond.