a1 Division of Psychology, School of Humanities and Social Sciences, Nanyang Technological University, Singapore 637332, Singapore.
a2 Evolutionary Morphology Section, Primate Research Institute, Kyoto University, Japan
a3 Primate Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
Animal traditions can affect survival by improving how individuals use their environment. They are inherited through social learning and are restricted to small subpopulations. As a result, traditions are rare and their preservation needs to be considered in biodiversity conservation. We studied Burmese long-tailed macaques Macaca fascicularis aurea living on Piak Nam Yai Island in Laem Son National Park, Thailand, which maintain a rare stone tool-using tradition for processing hard-shelled invertebrate prey along the island's shores. We found the population had 192 individuals in nine groups and most individuals used stone tools. This population is under pressure from the local human community through the development of farms and release of domestic dogs Canis familiaris onto the island. The level of anthropogenic impact varied in each macaque groups' range and juvenile–infant composition varied with impact. The proportion of young was smaller in groups overlapping farms and was negatively correlated with the amount of dog activity in their range. We also found that coastal use by macaques was negatively related to living near plantations and that the dogs displaced macaques from the shores in 93% of their encounters. We conclude that human impact is negatively affecting Piak Nam Yai's macaques and are concerned this could disrupt the persistence of their stone-use tradition. we discuss the impact and the potential consequences, and we recommend better protection of coastal areas within Laem Son National Park.
(Received October 12 2011)
(Revised December 13 2011)
(Accepted February 07 2012)
(Online publication August 14 2013)