Multi-scalar Approaches to the stable isotope ecology of late Quaternary Proboscideans in the Midcontinent

Stable isotopes of mammoths and mastodons have the potential to illuminate patterns in late Glacial landscapes and megafaunal population dynamics as these species approached extinction. The ecological factors at play in this extinction remain unresolved. Stable isotopes of bone collagen (δ13C, δ15N) and tooth enamel carbonate (δ13C, δ18O, 87Sr/86Sr) in late Glacial proboscideans from the Midwest, USA are leveraged to examine ecological and behavioral changes in these species during the last glaciation. Mammoth and mastodon δ13C values suggest they are flexible mixed feeders with significant C3 contributions to their diets. Bone collagen δ15N is also highly variable throughout this period. However some mastodons exhibit low δ15N values during the Bolling-Allerod. These low values could be explained by invoking changes in individual life histories (i.e., age at weaning), the expansion of available ecological niches, or both, metabolic compensation, or a mixture of these processes. Serial enamel samples show large differences between interglacial, mid-Wisconsin, and late Glacial mammoth oxygen isotope values. Finally, a new micro-milling approach to sampling mammoth tooth enamel is used to examine the life histories of two Missouri mammoths to provide nuanced, seasonally-resolved paleoecological information.