Of islands and dogs: Ethnohistoric and isotopic pathways toward understanding past dog diet in tropical Oceania

European accounts often state that the dogs of Oceania were fed plant foods such as breadfruit, coconut, yams, and taro. Some sources also reference dogs eating fish or taking on the roles of scavengers and hunters. Collectively, these accounts suggest that dogs' diets varied across the Pacific. As dogs are omnivorous, and can survive on a range of diets, it is likely that the local ecological, geological, and cultural setting influenced dog diets on different islands and in different island groups. Here we present a multi-isotopic Bayesian model for diet reconstruction from archaeological dog remains from Rakahanga Atoll, Cook Islands. We compare this novel dataset to extant datasets from differing island types (volcanic, coral, and mixed) to estimate the proportion of the animals' diets derived from marine sources, along with the trophic level of consumed animals. Our findings suggest that, while outliers exist, the majority of dogs from a given island share similar isotopic signatures. These signatures, however, differ between islands, even those of the same type. This indicates that island type may be a poor predictor for dog diet relative to other factors such as local human subsistence practices.