Paleobiologic interpretation of C, N, and O isotopes of Mammuthus primigenius tusks from Yakutia, Mainland Siberia

By Brad West
Whitman College, Walla Walla WA

Chemical changes in dentine layers in mammoth (Mammuthus primigenius) tusks can be used as a proxy for environmental conditions.  We report stable carbon, nitrogen, and oxygen isotope compositions (δ13C, δ15N, δ18O), growth increment profiles, and radiocarbon ages, of four tusks from Yakutia, mainland Siberia.  C and N isotopes show significant intra and inter-annual variation, implying mammoth diet changed both within and between years.  Using C isotopes, we calculated that mammoth diet was nearly entirely C3 plants.  The δ18O values of the tusks were used to calculate the δ18O value of meteoric water, which shows that the longitudinal meteoric water gradient of the Late Pleistocene was similar to the modern gradient.  Combining these data with published isotope values show that while diet varied significantly within individuals, no species-wide changes relate to extinction patterns, suggesting that climate change may not have been the primary factor in mammoth extinction.