Stable isotope analysis of Pacific rat (Rattus exulans) from archaeological sites in Mangareva (French Polynesia): The use of commensal species for understanding human activity and ecosystem change

Abstract

Stable carbon and nitrogen isotope analysis was applied to archaeological specimens of the commensal Pacific rat (Rattus exulans) to investigate nutrient fluxes in prehistoric socio-ecosystems on Mangareva (Gambier Islands) and their implications for anthropogenic environmental change. The Pacific rat – ubiquitous in Polynesian archaeological sites – is characterised by low dietary selectivity and a limited home range, making it an ideal candidate for assessing changes in island food webs. Temporal trends in diet-derived bone collagen δ¹³C and δ¹⁵N values are assessed from three sites: The Onemea Site, Taravai Island (TAR-6), Nenega-iti Rockshelter, Agakauitai Island (AGA-3) and Kitchen Cave Rockshelter, Kamaka Island (KAM-1). An overall trend of decreasing δ¹⁵N values in rat bone collagen over time reflects archipelago-wide changes to island socio-ecosystems most likely resulting from seabird population declines. Differences in site function and human activity may have also influenced local rat dietary patterns. Stable isotope analysis of the Pacific rat provides a low-impact line of evidence towards the reconstruction of human-centred food webs and the flow of nutrients within island socio-ecosystems.

Keywords:

• Rattus exulans
• Stable isotopes
• Mangareva
• Seabird extirpations
• Human ecodynamics
• Nutrient flows

Acknowledgements

Archaeological excavations in Mangareva were funded by U.S. National Science Foundation (NSF) Grants [BCS-1030049 and CNH-1313830] to Kirch, while the laboratory analysis of stable isotopes was supported by an NSF Doctoral Dissertation Research Improvement Award [BCS-1452364] to Kirch and Swift. Additional support was provided by the NSF Graduate Fellowship Program [Grant No. DGE 1106400] and from the Stahl fund of the U.C. Berkeley Archaeological Research Facility. Permission to conduct archaeological excavations in Mangareva was granted by the Service de la Culture et du Patrimoine of the French Polynesian government. We thank those who provided assistance in amassing these Pacific rat assemblages, especially our gracious hosts Edouard and Denise Sanford on Taravai Island and Tihoni Reasin on Kamaka, as well as Tepano and Helene Paeamara, and the other members of the 2012 and 2014 Mangareva excavation teams, Guillaume Molle, Jennifer Kahn, Alex Baer and Rose Guthrie. Todd Dawson, Stefania Mambelli and Paul Brooks of Berkeley's Center for Stable Isotope Biogeochemistry provided assistance in stable isotope preparation and analysis. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Supplementary data

The supplemental data for this article can be accessed at http://dx.doi.org/10.1080/14614103.2016.1216933.