Tracking possible decline of woolly mammoth during the Gravettian in Dordogne (France) and the Ach Valley (Germany) using multi-isotope tracking (13C, 14C, 15N, 34S, 18O)

The woolly mammoth (Mammuthus primigenius) was an emblematic and key species of the so-called mammoth steppe ecosystem between ca. 110,000 and 12,000 years ago. Its contribution to human subsistence during the Gravettian period as source of raw material was documented in southwestern France and southwestern Germany, with some evidence of active hunting in the latter region. However, decreasing genetic diversity and increasing indications of nutritional stress point to a likely decline of this megaherbivore. The specificity of the ecological niche occupied by the woolly mammoth is clearly reflected by their collagen C-13 and N-15 abundances (delta C-13(coll) and delta N-15(coll)), measured on skeletal remains of the typical mammoth steppe. The abundances of carbon-13 in mammoth collagen are comparable to those of other grazers like horse (Equus sp.), while the nitrogen-15 abundances are significantly higher (about 3 parts per thousand) than in the other herbivores, either horse or reindeer (Rangifer tarandus). During the Aurignacian and Gravettian occupation at Geissenklosterle in the Ach Valley (Germany), the mammoths had the expected stable isotope signature, but the nitrogen-15 of horses showed an unexpected overlap with those of the mammoth. This unusual pattern was already occurring during the Aurignacian, while the oxygen-18 abundances in bone phosphate (delta O-18(bp)) of horse and reindeer were unchanged between Aurignacian and Gravettian periods, which rules out significant change in environmental and climatic conditions. Thus, we hypothesize that during the Aurignacian and Gravettian, the ecological niche of mammoth was intact but not occupied intensively by mammoths due to a decline in their population. This decline could be tentatively explained by human pressure through hunting. In Dordogne (France), decreasing horse and reindeer delta N-15(coll) values coeval to decreasing horse delta O-18(bp) values between the Aurignacian and the Early Gravettian periods reflected a clear change in the environment, while no contrast in delta N-15(coll) values was observed between the Early and Final Gravettian at the Abri Pataud. The mammoth of Dordogne yielded slightly higher delta N-15(coll) values than expected, probably as a consequence of the nursing effect since all the analyzed samples were ivory instead of bone. The direct dating and sulphur-34 measurement on the ivory of the Early Gravettian at Pataud showed that almost all of them were of contemporaneous and local origin. Significant contrasts in delta S-34(coll) values were found between the Dordogne and the Ach Valley for the same herbivores species, which confirms the potential of sulphur-34 in collagen as a mobility tracker. (C) 2014 Elsevier Ltd and INQUA. All rights reserved.