Diachronic reconstruction of palaeoclimates and diet through stable isotopes (δ13C and δ18O) and 2D geometric morphometrics from cave bear (Ursus spelaeus) dentition

Abstract

Europe experienced periods of significant climatic fluctuation during the late Pleistocene, which is likely to have led to environmental stress on many species, including the extinct cave bear Ursus spelaeus. We investigated temporal variation in carbon and oxygen isotopic values extracted from dental enamel of U. spelaeus specimens from multiple stratigraphic units within Scladina Cave, Belgium, in conjunction with dental morphology, which we quantified using 2D geometric morphometrics to test the hypothesis that Pleistocene climatic changes impact phenotypic variation and feeding ecology of extinct megafauna. Size and shape of the second lower molar differ in cave bears across several stratigraphic units, even for short temporal gaps between sediment depositions (∼3ky). Ursus spelaeus from Scladina exhibited low δ¹³C values comparable to that of contemporary herbivores from the same sequence, suggesting an herbivorous diet for the species throughout the temporal sequence. Climatic change had an impact on size and diet, with larger dentition relating to previously suggested colder environmental periods. The existence of these periods was further supported by our δ¹³C and δ¹⁸O measurements. Warmer periods were indicated by higher δ¹⁸O values and correlated with lower δ¹³C values indicative of a diet enriched in plant sources from more forested environments. The environmental variation through the studied sedimentary units of Scladina Cave is discussed and interpreted alongside previously produced palynological results for units herein. Our results support previous suggestions that cave bears from Scladina Cave had a herbivorous diet, while further strengthening the current stratigraphic interpretation of the cave.