Isotopic evidence for a diet shift in a Pleistocene sub-adult mastodon from the Brazilian Pampa

Abstract

ABSTRACT Palaeoecological studies on South American mastodons using stable isotopes from isolated teeth indicate variable diets, but represent only a short portion of the total lifetime of the studied individuals. Here is presented an analysis of the carbon (δ13C) and oxygen (δ18O) isotope ratios on three molariforms (m1, m2 and m3) from the jaw of a sub-adult mastodon found in southern Brazil, aimed at understanding its long-term feeding habits. The individual died at about ~26-30 years of age, and the isotopic signal recorded in each tooth spans up to ~3-5 years based on estimates of tooth development from enamel thickness, but apparently there were significant temporal gaps (>5 years) between the mineralisation of each tooth. The δ18O did not vary significantly between the teeth, but the more positive δ13C in the m1 indicates a diet with higher proportion (>30%) of C4 plants, whereas the m2 and m3 indicate considerably less (<20%) C4 plants ingested. This diet shift could have been the result of ontogenetic development, migration, or some disturbance in plant communities driven by environmental stresses. The results indicate that mastodons were able to change their diets at shorter timescales than can be addressed from the analysis of isolated teeth.