Primate Archaeology Research Group, School of Archaeology, University of Oxford, Oxford, United Kingdom
Lars Kulik
Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
Tomos Proffitt
Primate Archaeology Research Group, School of Archaeology, University of Oxford, Oxford, United Kingdom
Suchinda Malaivijitnond
Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand; National Primate Research Center of Thailand-Chulalongkorn University, Saraburi, Thailand
Michael Gumert
Division of Psychology, School of Humanities and Social Sciences, Nanyang Technological University, Singapore, Singapore; Primate Archaeology Research Group, School of Archaeology, University of Oxford, Oxford, United Kingdom; Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
Tool use has allowed humans to become one of the most successful species. However, tool-assisted foraging has also pushed many of our prey species to extinction or endangerment, a technology-driven process thought to be uniquely human. Here, we demonstrate that tool-assisted foraging on shellfish by long-tailed macaques (Macaca fascicularis) in Khao Sam Roi Yot National Park, Thailand, reduces prey size and prey abundance, with more pronounced effects where the macaque population size is larger. We compared availability, sizes and maturation stages of shellfish between two adjacent islands inhabited by different-sized macaque populations and demonstrate potential effects on the prey reproductive biology. We provide evidence that once technological macaques reach a large enough group size, they enter a feedback loop – driving shellfish prey size down with attendant changes in the tool sizes used by the monkeys. If this pattern continues, prey populations could be reduced to a point where tool-assisted foraging is no longer beneficial to the macaques, which in return may lessen or extinguish the remarkable foraging technology employed by these primates.
