Excavation underway on the south-eastern coast of Piak Nam Yai, December 2013

The latest PRIMARCH field season in southern Thailand was successfully wrapped up just before Christmas 2013. Our focus for this season was on recovery of wild macaque stone tools in two contexts: (1) following direct observations from a boat of unhabituated macaque behaviour; and (2) through archaeological excavations at the island of Piak Nam Yai (PNY), in Ranong District. Over a period of two months, members of the PRIMARCH team including Alejandra Pascual-Garrido, Hannah Mosley and Michael Haslam were joined by volunteer Kathryn Reusch and site director Michael Gumert, as we looked to expand on our previous work that demonstrated how macaque tools can be identified from the ways they are damaged during use (Haslam et al. 2013 PLoS One).

We conducted our first excavations in some of the beach sand areas of PNY, building on earlier work among the PNY mangroves, and found evidence of past tool use as well as a collection of shells that we will be using for radiocarbon dating. As is typical for this island, our sites were covered by a metre or more of water twice daily during high tide, which added an extra element of urgency to each day’s work. We also carried out an initial study of the oysters that form the primary focus for tool use among the macaques (see Gumert and Malaivijitnond 2012 for more information about the diet of these monkeys). We are interested in what the costs and benefits of tool use may be for the PNY macaques, given that they are the only known stone-tool-using Old World monkeys, and the nutrition and energy returns they get from their prey may be an important part of the benefit side of that equation.

We will be posting further details on this site as these studies progress, along with updates on recent studies from all of the species involved in the primate archaeology project.


Gumert M, and Malaivijitnond S. 2012. Marine prey processed with stone tools by Burmese long-tailed macaques (Macaca fascicularis aurea) in intertidal habitats. American Journal of Physical Anthropology 149:447-457.

Haslam M, Gumert M, Biro D, Carvalho S, and Malaivijitnond S. 2013. Use-wear patterns on wild macaque stone tools reveal their behavioural history. PLoS One 8:72872.