This dissertation applies stable carbon (δ13C) and nitrogen (δ15N) isotope analysis to archaeological specimens of the human-transported Pacific rat (Rattus exulans) to investigate prehistoric patterns of subsistence, site use, and long-term socio-ecosystem dynamics on Polynesian Islands. The Pacific rat is a small commensal species characterized by low dietary selectivity and a limited home range. Its close association with past Polynesian peoples—and ubiquity in Polynesian archaeological sites—suggests that dietary change in this species can provide insight into changing island landscapes and human subsistence regimes. Pacific rat bone collagen δ13C and δ15N values were compared across three contrastive island socio-ecosystems: Mangareva, the Marquesas, and Tikopia.

Spatiotemporal trends in Pacific rat stable isotope ratios are related to localized changes in human activity and subsistence practices, as well as global ecosystem processes which include avifaunal extinctions, resource depression, and soil nutrient cycling. On Mangareva, temporal variations in δ13C and δ15N values were 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). Declining δ15N values through time at all three Mangarevan sites reflect archipelago-wide socio-ecosystem changes related to site activity and avifaunal population declines. At the Hane dune site, Ua Huka Island (Marquesas), shifts in rat diet provide insight into changing Marquesan settlement and subsistence practices. On the Polynesian Outlier of Tikopia, a 650-year period of stability in rat bone collagen δ13C and δ15N values during the Kiki Phase (800-160 BC) suggests that mechanisms for long-term socio-ecosystem sustainability have been in place on the island for over 2000 years. These results demonstrate the capacity for stable isotope analysis of the Pacific rat to provide a new, low-impact line of evidence towards reconstructing localized patterns of site use, subsistence practices, and island ecology.