Importance of pigtailed macaques (Macaca nemestrina leonina) in seed dispersal and impact on the ecological balance of the tropical rainforest at Khao Yai National Park, Thailand

The tropical rain forest is maintained thanks to a precarious balance placed under the yoke of interactions between the various animal and plant species which compose it. Among them we can find those implying plants and frugivores. Although its diet is largely frugivorous, the pigtailed macaques (Macaca nemestrina leonina) have often been categorized as seed predators. However their morphology, behaviour and ecology suggest they could actually be a key-species in the dispersion of many plant species. A preliminary study by Latinne & al (2007) supported this hypothesis. The study we are planning now in continuity of Latinne’s study will take place in the Khao Yai National Park, Thailand, for three years and will focus on a troop habituated to humans. In order to establish the importance of the pigtailed macaques in the maintenance and the regeneration of the tropical rain forest, we will try to evaluate their capacity of being good seed dispersers. To do so, we will study: 1) the spatiotemporal distribution, the productivity and the characteristics of the plant species present on the home range of the studied troop, 2) the ranging patterns of the macaques within their home range, 3) their feeding behaviour, notably the fruit selection and the various modes of processing seeds, and finally 4) their impact on the viability and the germination potential of seeds. This study will require both direct observations of the macaques and semi-experimental procedures in the field, as well as laboratory control of some seed parameters. We hope the clarification of the macaques’ seed dispersal behaviour would help to re-evaluate their conservation status by recognizing them a paramount role in the maintenance of the tropical rainforest.